Add further information to display: unit & building stats

* We now extract unit & building stats (health, attack and armour) from the files and send it to the client
* This is so it may be used in the tooltip
   - The usage in the tooltip is not yet implemented, yet
* This commit also includes the rank icons from 0AD-core
Display armour and attack stats of structures and units in tooltips

* The display of these stats is currently text-based only and isn't very pretty.
* The php code also now fetches unit attack stats properly, checking parent templates when necessary
Pass tooltip string from datafiles to client

* Units/Structures/Techs have tooltip messages defined in their files.
* This is now read and passed to the client for use in the mouseover tooltips
Display tooltip string in tooltip

* Also adjusts the armour/attack stats vertical alignment
Consolidate stats elements

* In the tooltip, the armour and attack stats were being presented as a text object inside a group.
* Now they are combined into one text object, with no group
* This will/should help with later additions
Load and show healers' stats

* If a unit has the ability to heal others, this is now shown in the stats object in the tooltip