Added support for capitalization when searching bookmarks
When the user inputs no capital letters then all bookmarks will be matched
disregarding their capitalization. If any of the letters the user inputs
are capital letters then only bookmarks with the exact same capitalization
as the entire input string are matched.
Reviewed By: nmel, martinkostolny, asensi
Differential Revision: https://phabricator.kde.org/D11906