Client|UI|GLTextComposer: Better way to set partial range of lines

GLTextComposer also needs to allocate only the visible lines, so just
doing the geometry is not enough.
libdeng2|Range: Added isEmpty() method
Merge branch 'master' of ssh://github.com/skyjake/Doomsday-Engine
Merge branch 'master' of ssh://github.com/skyjake/Doomsday-Engine
Codex: Fine-tuning related tags
Codex: Added breakdown of authorship for each tag

Showing percentage of commit authors.