improve bookmark UI
add code that can bookmark multiple files, also if they are not open (and do some cleanups in the meanwhile)
add option to make search bookmarks temporary or permanent
implement a color for each external bookmark command. fix some bugs on the go
you can set a color for a auto generated bookmark now
fix compile warnings
temp bookmarks have a different color now (not yet configurable, so not good for dark themes)
fixes a bug in search results in the outputpane (they were not escaped for markup) and includes more bookmarkchanges