Pass the custom data install path to the compiler

The CUSTOM_DATA_INSTALL_PATH constant is checked at different
places in the code but was not actually passed to the compiler.
This resulted in searching the data files in /usr/games instead
of /usr/share/games/megaglest (in Ubuntu and Debian).

This commit also fixes setting the variable. It is still wrong
for Apple I think. But I can not test it.
optional start-ep tag implemented
fixed an unimported copy&paste tag :) had no influence afaik but still
better like this
Merge pull request #14 from FreshDumbledore/develop

Start EP can be set
testing version of multiple projectiles
multishot with more than one attack particle system
use  a bool instead of a (unused) pointer.
multi projectiles with different timings and particle systems
Start ep now an argument of max-ep

Syntax is `<max-ep value="500" start-value="250" />`
Implemented start percentage for EP

Note that start-value and start-percentage (both are attributes of the
max-ep tag) are mutually exclusive. If they both exist, then
start-percentage is used.
Error checking now active for start-ep

You can no longer have both start-value and start-percentage.
multishot with multi sounds and possible camerashake on projectile impact. 

Still work in progress!
Implemented starting value for HP

Same syntax as for EP:

    <max-hp value="1000" regeneration="1" start-percentage="1.0" />

Where `start-percentage` can be replaced by `start-value` to use an
absolute number. Note that unlike EP, HP defaults to the max-hp value
*before* upgrades are applied. This behavior is not changed. To make units
spawn with their fully upgraded HP, set their start-percentage to 1.0.
new style projectiles must have a particle system
Splash was broken and destructor needs to cleanup more
First, basic looting implementation

Only absolute values are obtained for now, no loss.
Implemented rest of resource amount/loss attrs
Added setting to disable going into negatives

After all, how does one loot what the other faction does not have? Still,
could be useful for some places, by forcing the opponent to go into
"debt".
No looting if you attack units in same faction
Lootable resources now checks for dups