Set variables for Bootstrap to inherit

[PhantomWatson]

Problem

Right now, link colors are defined in datacenter.less, but overwritten by Bootstrap's link colors defined in variables.less when Bootstrap classes are used.

Solution

1. Create a copy of variables.less for the Data Center plugin
2. Adjust CRI (and any other CakePHP 3 websites) to import this file and not Bootstrap's variables.less file
3. Use these variables in datacenter.less and each CakePHP 3 site's own style.less file