FIX: Consistenly look for fonts in special//home, then special://xbmc
fix #3166: use URIUtils::AddFileToFolder
Standardize ReplayGain case

ReplayGain is spelled with CamelCase. Strings around the settings
pannel should match that.
http://en.wikipedia.org/wiki/ReplayGain
Music search bugfix

CDirectoryHistory::ClearSearchHistory misused vector::iterator::operator++
in conjunction with vector::erase such that it iterated beyond the end of
the vector if there was a previous music search, resulting in a segfault.
End effect: you could only do one search. Replaced with std::remove_if.
Merge pull request #3252 from bavison/music_search_bug

Music search bugfix
Merge pull request #3275 from yoavf/master

Standardize ReplayGain case
Merge pull request #3166 from koying/fixfontpath

FIX: Consistenly look for fonts in special//home, then special://xbmc
fixed, add missing UnregisterCallback for XBMCHelper