ajaxCategories fixes based on review in r93351 CR:

ajaxCategories fixes based on review in r93351 CR:
* Using typeof check in clean()
* Use mw.Title to get page title from fullpagename instead of split(':')
* replaceNowikis() and restoreNowikis()
 - Improve documentation
 - Moved dash in the UNIQUEKEY to between the id and the incrementing integer, and made it start with an empty string (so that all following concatenations are toString'ed).
* makeCaseInsensitive(): Moved the wgCaseSensitiveNamespaces-check out and wrapped it around the caller instead. Also cached the outcome of "Is category namespace sensitive ?".
* createButton(): text-argument is indeed text, not html. Applying html-escaping.
* resolveRedirects():
 - Replace access to private property _name of mw.Title with function getMainText().
* handleCategoryAdd() and handleEditLink():
 - Restructure title-handling (no local replace() calls and clean(), let mw.Title handle it)
 - Renaming arguments and documenting them better
 - Renaming local variables and removing redundant parts
 - Preserving sortkey as sortkey as long as possible without the pipe
 - Calling the combination of sortkey and leading pipe 'suffix' instead of, also, sortkey.
* createCatLink():
 - Remove the sanitizing here, the string passed is already clean as it comes from mw.Title now
 - Using .text() instead of .append( which is .html-like), category names can contain special characters.
* containsCat():
 - Using $.each instead of [].filter. Stopping after first match.
* buildRegex(): Allow whitespace before namespace colon, and allow whitespace after category name (but before ]] and |..]])

Additional changes not for any function in particular:
* Literally return null in $.map callbacks.
* Using the existence-system of mw.Title instead of passing around booleans everywhere
** Removed 'exists' argument from the resolveRedirects() and handleCategoryAdd() functions, instead checking .exists() of the mw.Title object.
* Passing and using mw.Title objects where possible instead of converting back and forth between strings and objects etc.
* Using "TitleObj.getUrl()" instead of "catUrl( titleString )". Removed now unused catUrl() function.
* To improve readability, renamed local uses of 'var that = this' to 'var ajaxcat = this'.
* Syntax error fixes (.parent -> .parent())
* Merging var statements
* Renamed generic members of 'stash' from 'stash.summaries' to 'stash.dialogDescriptions' and 'stash.shortSum' to 'stash.editSummaries'. dialogDescription is always HTML (input should be escaped before hand)