Fixes #5190: Correctly strips duplicate (type)/ from simplecache URL
Fixes 5013: Uses menu system for "Register" and "Lost password" links.
Fixes #5342: Login completes if [login, user] event redirects
updated changes file for the 1.8.15 release
Updated commit for messages_get_unread function

replaces https://github.com/Elgg/Elgg/pull/5396#issuecomment-16930955

I don't know the prefered process to edit a submitted commit (directly on the website), please tell me if there's a better way than adding a new commit ?

Thanks
cleaned up caching code - deprecated several functions
Merge pull request #5192 from mrclay/5190-sc-url

Fixes #5190: Correctly strips duplicate (type)/ from simplecache URL
made php's get simple cache function match js one
Merge pull request #5344 from mrclay/5342

Fixes #5342: Login completes if [login, user] event redirects
Merge pull request #5321 from juho-jaakkola/login_menu

Fixes 5013: Uses menu system for "Register" and "Lost password" links.
modified navigation private functions to use _elgg namespace
Fixes #5103 adds viewtype to cache url regex
Fixes #5285 throw exception if relationship name is greater than 50 chars
Fixes #4805 removing exit since cannot reproduce - will investigate further if someone reports again
Fixes #5407 colorbox theme
removed example files from colorbox
upgraded colorbox to 1.4.15
upgraded ckeditor to 3.6.6.1
added .gitignore file for ckeditor vendor files that we don't want to include
removed version number for imgareaselect jquery plugin directory name