Normalize the @gray[-xxxx] variable definitions in several variables.less files to bring most themes in-line with standard Bootstrap's variable.less file.  Take note: no values are changed; just assigning #000 to @gray-base in the @gray[-xxxx] section.
Merge pull request #351 from StevenBlack/normalize-gray

Normalize the @gray[-xxxx] variable definitions in several variables.les...