Added documentation for dirTree, close #3
Missing docstrings added to settings.py for #4
Missing docstrings added to dirTree.py for #4
Missing docstrings added to guiManager.py and plugins.py, close #4
Merge branch 'doc' into devel

Conflicts:
	settings
	settings.py
Created doc and template for dirFrame
Widgets for dirFrame created
More work on dirFrame & windows subtitle now shows path to active folder
Thumbnails now show in correct size.
dirFrame now shows main directory title and emits signals file-selected & file-activated
fileManager plug-in added.
Gnome thumbnailers now work.
File activate problem in fileManager.py fixed
dirFrame wouldn't show onDirChange, fixed
History plug-in added with most basic functionality. Plug-in development tutorial created (but incomplete), bug dir-change response of dirTree fixed
Spinner shows in title while loading content