Major tasks undertaken in this patch:
* New format_text argument, overflowdiv.
* New page layout Report.
* Review of all format_text calls.
* Added support for the report layout to all themes.
* Changed forum post display from tables to divs.

MDL-23784 finally getting rid of all legacy .gif and .png extensions, yay! fixing issues with incorrect & in JS code

MDL-22001 filter_text() and filter_string() now use context parameter instead of courseid, PAGE->context is used only as a fallback; moved comment stuff away from format_text() because it does not belong there; filterlib is not using courseid except for legacy filters; fixed coding style in filters;Êimproved php docs; fixed upgrade of filters (should be in plugins, not core)

MDL-22950 adding new component column to the files table, unfortunately this change requires changes in all 2.0dev code, please review all custom code that was already upgraded to 2.0; fixing multiple problems and regressions in mod/assignment

New string is available. Use get_string('labelsep', 'langconfig') to be used
as a separator between a label and the labelled text. If you want to
produce <label> HTML element, you may be interested in the new
html_writer::label() method. Simple selects and URL selects now use it.

There are bambillion places where ': ' is hardcoded as a separator. I do
not think we have to fix them manually now (and mass search and replace
would be tricky) but everybody should stop adding new.

Do not abuse 'labelsep' for any other purposes. Note that it may not be
colon in some languages or sites.

MDL-22712, added admin options to enable/disable comments in blog, and a switch to show/hide comments count

blog MDL-22058 Fixed up blocks using the naughty blog_get_headers method, recent blogs and blog tags

MDL-21655 big scary enrolment and roles improvements - see tacker for list of changes, includes other minor fixes too

* class html_component does not exist any more
* class html_table rendered via html_writer::table()
* html_table, html_table_row and html_table_cell have public $attributes property to set their CSS classes
* dropped rotateheaders feature, should be added again after more research of possible ways (<svg> is not nice IMHO)
* dropped possibility to define CSS classes for table heading, body and footer - can be easily done and better done using just table class and context

MDL-21233 moodle_url improvemewnts, code simplification, more diagnostics; fixed several regressions

MDL-21235 new link method in html_write, partinally replaces old html_link, going to add new action_link soon

MDL-21198 improved/simplified $OUTPUT->user_picture() + regression fixes, performance fixes and detected performance problems when printing user avatars

MDL-19754 MDL-8776 MDL-19678 MDL-20314 Converting old post table to blog_entries, upgrading blog code accordingly, and tags in tag_instance table

MDL-19676 Put association section in advanced items for edit form, corrected bug in group listing, enabled commenting