If you want to make changes to the .css generated from these .less files then you
need to use a LESS Compiler. Details on specific compilers and how to install them
can be found at http://docs.moodle.org/dev/LESS

Requirements:
nodejs, npm, grunt-cli.

Installation:
node and npm: instructions at http://nodejs.org/
grunt-cli: `[sudo] npm install -g grunt-cli`
node dependencies: run `npm install` in the root directory.

Usage:
Default behaviour is to watch all .less files and compile
into compressed CSS when a change is detected to any and then
clear the theme's caches. Invoke either `grunt` or `grunt watch`
in the theme's root directory.

To separately compile only moodle or editor .less files
run `grunt less:moodle` or `grunt less:editor` respectively.

To only clear the theme caches invoke `grunt exec:decache` in
the theme's root directory.

Additional information about the Moodle bootstrap base theme can be found at
http://docs.moodle.org/dev/Bootstrap