Adds tpope Abolish plugin for better abbreviates and substituions
Convert abbreviations to use tpope's vim-abolish

https://github.com/tpope/vim-abolish provides some tools for more
concisely defining abbreviations. This converts from vim's built in
abbreviation command to use the Abolish command included with the
plugin.

Because the vimrc is loaded before plugins, this also required that
abbreviation definitions be moved from a file loaded at vimrc sourcing
to a file in .vim/after/plugin so that the Abolish command would be
available.
Keep abbreviations at top level of vimdir, but source it from a file in after/plugin
Condense function abbreviation definition using Abolish
Condense more abbreviations with Abolish