Improve UI for Special:Recentchanges and Special:Recentchangeslinked.

Improve UI for Special:Recentchanges and Special:Recentchangeslinked.
* Allow configuration of the default limit and days links with the variables $wgRCLinkLimits and $wgRCLinkDays.
* When selecting a limit and a days on the special pages, if you use a number not within the default list it will be added to the display.
** The selected limit and days is bolded. (This can be considered the first step for bug 3327)
* Optional other configuration option $wgRCFilterByAge, when enabled the list of days will be filtered so that only links within what $wgRCMaxAge says will be stored in the database will be displayed. Note that this is disabled by default because MediaWiki doesn't quite seam to trim out old entries as quickly as $wgRCMaxAge says it should be and some people appear to use the extra 30days links to display older entries even though $wgRCMaxAge is set to 7days on said wiki.

This should also solve bug 9257.