Always display the sign column

If I don't, then when vim-gitgutter activates, it pushes my code to the
right.
Disable \\ in vim-commentary, to get used to `gc`
Ignore .projections.json
Add filetype to Vim statusline
Allow folding single lines (useful for TOC-style)
Don't automaticaly fold Git commit diffs
Add `cd` completion for common directories