[#32063] Added support to change link color in isis template (backend)

Before:

![before](https://f.cloud.github.com/assets/441774/1103629/bb72afc6-18b8-11e3-93ed-39fbddc382a8.png)

After:

![after](https://f.cloud.github.com/assets/441774/1103630/c3faffb8-18b8-11e3-8f56-b1144e638adc.png)

Tracker: #32063
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32063&start=0