* Per my CR comments on r44560: merged FileCache into RepoGroup and fixed wfFindFile...

* Per my CR comments on r44560: merged FileCache into RepoGroup and fixed wfFindFile() global function bloat. Did not port unused functions such as the batch loading functions.
* Fixed the formal parameter bloat in the file finding functions by making wfFindFile(), RepoGroup::findFile() and FileRepo::findFile() take an associative array of options instead of a rapidly growing collection of formal parameters. Maintained backwards compatibility for the $time parameter, which was the only one used in an extension.
* Took the advice of the todo comment on FileRepo::findFiles() and implemented a calling convention for specifying times (and other options)
* Removed the file object cache from Parser, redundant with the RepoGroup file cache
* Deleted clueless and non-functional LocalRepo::findFiles(). Does not respect redirects, deletion bitfields, or anything else nuanced about FileRepo::findFile(). Does not have the same calling convention as FileRepo::findFiles().