This allows you to control what search engines for project-search
commands (bound to SPC / p) to try, and in what order. If you didn't
want to use ripgrep, for instance, remove 'rg from these variables, or
move it to the end of the list.
Adds +helm/project-search, as well as +helm/ag and +helm/ag-from-cwd,
and variants for rg, pt and grep/git-grep, to mirror the functionality
available to :completion ivy.
Also updates the evil ex commands and keybinds
