Rename vim-sbt submodule

It is supposed to be https://github.com/derekwyatt/vim-sbt, but
https://github.com/dscleaver/sbt-quickfix overwrites it when
install-vim-plugin is called.
Add DiffOrig command
Improve color scheme in vimdiff

But it still is pretty bad
Update idris-vim plugin
Rename vim-basic-sbt submodule back to vim-sbt

I'll just remember not to run install-vim-plugin from the sbt-quickfix
plugin, since it overwrites this dir.
Add vim-abolish submodule
Add vim-eunuch submodule