Add ColorKeyword linter

Add a linter to detect when using one of the extended color keywords
instead of a hexadecimal value.

The representation of these colors usually require more bytes than a 4-7
character hex code.

Change-Id: I2ef7b28fa28afc5c09b1b68a65305bec144ea878
Reviewed-on: https://gerrit.causes.com/27825
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: jenkins <jenkins@causes.com>