Having had one subtle bug cased be this, I decided to do a search and
fix all of these.

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

Shortanswer question type converted to use extra question fields.
Signed-off-by: Oleg Sychev <oasychev@gmail.com>

This commit includes minor bug fixes elsewhere in the system.

MDL-20700 coding style cleanup - cvs keywords removed, closign php tag removed, trailing whitespace cleanup

question editing: MDL-18035 Nice refactoring from Oleg Sychev that saves 50+ lines of code between the various editing forms.

MDL-8475 - Better handling of blank answer - further changes to make it even more robust. Also, make the same changes to the shortanswer question type that were already made to the numerical question type.

MDL-12133 - Errors calling parent::validation in a moodle form subclass because the base class method signature was changed. This patch fixes all calls to parent::validation in the question editing forms. Merged from MOODLE_19_STABLE.

MDL-10786 - Short Answer questions will not allow 0 as the sole answer. Merged from MOODLE_18_STABLE.

Bug 2951 - correct PARAM_ types for answers to multichoice and shortanswer questions. Merged from OU Moodle.

MDL-8671 - better checking when creating short answer questions. Fix thanks to Joseph Rézeau. Merged from MOODLE_18_STABLE.

various formslib work including bug fixes for MDL-8039 id attribute collision between forms and page ids. Also added editor helpbutton. This is a fix for MDL-6941 need the ability to associate several helptopics with htmleditor. Also started on converting forms for question types to formslib.