Merge pull request #3619 from edx/markhoeber/documentatoin/online-help-system

Online help system
SymbolicResponse fix error message.
Merge pull request #3716 from edx/anton/i18n-symbolic-response

SymbolicResponse fix error message.
ORA2 release 2014-05-19
Add Croatian language
Update translations (autogenerated message)
Merge pull request #3771 from edx/sarina/051914-language-update

Sarina/051914 language update
Merge pull request #3768 from edx/will/ora2-release-2014-05-19

ORA2 release 2014-05-19
Allow creation of components on container page

This commit implements STUD-1490, allowing creation of components
on the container page. It also enables the delete and duplicate
buttons now that new content can be created that would benefit.

Note that it also creates shared functionality for adding components,
and refactors the unit page to use it too.
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Add unit tests for vertical and StudioEditableModule
Separate the view for container xblock when shown on unit page vs. shown on container page.
Add unit tests for child containers