Includes:
* update checker refactored to \core\update\ namespace
* plugininfo classes refactored to \core\plugininfo\ namespace
* plugin_manager renamed to core_plugin_manager
* redirect back to original page after plugin uninstall
* fixed assign subplugin uninstall
* move assign subplugins under the assignment in admin tree
* fixed plugininfo for all question related plugin types
* auth uninstall support
* added missing block dependencies
* added theme uninstall
* subplugin types are following the plugin on plugin overview page
* several performance improvements in plugin manager
* new warnigns when plugininfo are outdated or missing
* multiple fixes and other improvements

At the moment, when attempt is built on the last one, "not yet answered"
message is shown, which confuses many people. This patch modifies the state to
"complete" for attempt based on previous and modifies the output string.

Many thanks to Tim Hunt for guiding me through quiz infrastructure and some code
suggestions.

AMOS BEGIN
MOV [unknownorunhandledtype,qformat_blackboard_six],[unknownorunhandledtype,question]
AMOS END

AMOS BEGIN
 MOV [matcherror,question],[invalidgrade,question]
AMOS END

There were a number of lang strings in suboptimal places.
This commit fixes that, and also removed some unused strings.

AMOS BEGIN
 MOV [addmorechoiceblanks,qtype_multichoice],[addmorechoiceblanks,question]
 MOV [youmustenteramultiplierhere,qtype_calculated],[youmustenteramultiplierhere,qtype_numerical]
AMOS END

The settings control the display options used when a user
first previews a question in the question bank. Once a
user has previewed some questions, these are stored as user
preferences.

It may not seem worth making this configurable, but acutally
it is important when training new users to get them started
off using the right opitions.

It is useful, and possible, to update the display options without
restarting the question. You now only have to restart if you are
changing the maximum mark or the behaviour.

Without this, there are some interactions with the question that could
only be tested by adding the question to a quiz, which was a pain.

... but hide it in a collapsible region.

AMOS BEGIN
 CPY [shownumpartscorrect,question],[shownumpartscorrectwhenfinished,question]
AMOS END

When shortanswer, numerical, calculated and calculatedsimple questions
did not have a '*' match-anything answer, then any student response that
did not match any of the teacher-given answers were classified as
'[No response]', which was not right.

This patch fixes that. Such responses are now classified as
[Did not match any answer].

While I was doing this, I noticed that the display of tolerance
intervals for numerical questions in the response analysis was horrible,
so I improved it.

AMOS BEGIN
 MOV [selectcategoryabove,mod_quiz],[selectcategoryabove,question]
AMOS END

AMOS BEGIN
 MOV [noquestionsinfile,mod_quiz],[noquestionsinfile,question]
AMOS END

when an error occurs in the middle of processing responeses.

All the references to this sring were already referring to it in the new
place.

AMOS BEGIN
 MOV [cannotread,mod_quiz],[cannotread,question]
AMOS END

AMOS BEGIN
 MOV [categorymove,mod_quiz],[categorymove,question]
AMOS END

While doing this, I found various bugs in the manages question types admin page, and so fixed them, and updated the code
there to use $OUTPUT and html_writer.

AMOS BEGIN
 MOV [cannotdeletemissingqtype,admin],[cannotdeletemissingqtype,question]
 MOV [cannotdeleteqtypeinuse,admin],[cannotdeleteqtypeinuse,question]
 MOV [cannotdeleteqtypeneeded,admin],[cannotdeleteqtypeneeded,question]
 MOV [deleteqtypeareyousure,admin],[deleteqtypeareyousure,question]
 MOV [deleteqtypeareyousuremessage,admin],[deleteqtypeareyousuremessage,question]
 MOV [deletingqtype,admin],[deletingqtype,question]
 MOV [numquestions,admin],[numquestions,question]
 MOV [numquestionsandhidden,admin],[numquestionsandhidden,question]
 MOV [qtypedeletefiles,admin],[qtypedeletefiles,question]
 MOV [uninstallqtype,admin],[uninstallqtype,question]
AMOS END

AMOS BEGIN
    MOV [page-blog-index, pagetype], [page-blog-index, blog]
    MOV [page-blog-x, pagetype], [page-blog-x, blog]
    MOV [page-tag-x, pagetype], [page-tag-x, tag]
    MOV [page-course-view-weeks, pagetype], [page-course-view-weeks, format_weeks]
    MOV [page-course-view-weeks-x, pagetype], [page-course-view-weeks-x, format_weeks]
    MOV [page-course-view-topics, pagetype], [page-course-view-topics, format_topics]
    MOV [page-course-view-topics-x, pagetype], [page-course-view-topics-x, format_topics]
AMOS END

Also fix some minor bugs and unit tests.

This mostly involves moving lang strings around, but I don't have time to do an AMOS script now.