vim: fix vimrc, remove todo plugin, add lastplace

vim: fix vimrc, remove todo plugin, add lastplace

- comments were updated and some sections reordered
- removed todo.txt plugin as I have not used it in forever
- added lastplace plugin for missing cursor return in nvim
- removed vimStartup autocmd from defaults.vim, as lastplace plugin replaces it
- made commentary plugin optional and only load under vim, as nvim has built in
  comment handling now
- fix lots of autocmds to use the correct events and actually do things
- add autocmd to some options that needed it, such as autoindent under vim
- change default colorscheme to murphy
- modify space coloration logic and highlight group names
- add CTRL-L :noh to vim like with sensible.vim and nvim
- add a few new options to override sensible.vim if loaded (like in termux)