LFR Call to arms CTA

Added separate commands to search for Legion's Heroic Random dungeons. Once a CTA spot is found, an alert will fire off.

Here is an updated list of commands (as of v2) 

--- Raid/LFR CTA commands ---

/cta d = Find RF DPS CTA

/cta h = Find RF Healer CTA

/cta t == Find RF Tank CTA

--- Heroic CTA commands ---

/cta hd = Find RF DPS CTA

/cta hh = Find RF Healer CTA

/cta ht == Find RF Tank CTA

I also made changes to the buttons that pop up (resized them) and the printed messages the user will see.