[vim] Remove highlight abbreviations

Writing `highlight` instead if `hi` makes the code easier to understand.
[vim] Remove nocompatible since it's not necessary

Having a vimrc file automatically sets the nocompatible option, so
manually setting it is not necessary.
[vim] Change mappings to be non-recursive

Most normal mappings should be non-recursive (`nnoremap`). Mappings for
visual mode should be defined with `xnoremap`, since `vnoremap` also
referes to select mode.

Recursive mapping should be used when remapping <Plug> mappings, e.g.
the mapping for toggling comments.

More information:
- https://gist.github.com/romainl/9ecd7b09a693816997ba#file-vimrc-L82
- http://www.reddit.com/r/vim/comments/2qlt8j/antipattern_of_vimrc/cn7au7b
[vim] Remove unused function for renaming tabs
[vim] Move highlights to separate section

Also remove reduntant comments.
[vim] Move custom functions to separate section
[vim] Move autocommand groups to separate section
[vim] Right align comments

Move all comments from above the related line to the right side of the line.
[vim] Add mapping to toggle comments in visual mode
[vim] Move YOPO mappings to bottom of mappings list
[vim] Check if plugin is present before mapping
[vim] Remove duplicate mappings
[vim] Simplify NumberToggle function

It is possible to toggle boolean vim options by adding an exclamation mark after
the option, e.g.: `relativenumber!`
[vim] Use color numbers instead of color names