Initial
Better support for indentation options

Add functions SeIndentHard, SeIndentSoft and SeIndentMixed to set
correct indentation options (et, sw, sts, ts) for using, resp., all hard
tabs, all spaces and mixed tabs & spaces, to indent.
Each of these has a 'Setl' counterpart (eg. SetlIndentSoft) that only
sets the buffer-local options.
Add 'Maintainer' header to vimrc