Fixed cmake pch compilation when not builing from the top source folder.

This fixes #218 for me. Thanks to Gallaecio for poiting out. :)
Merge pull request #219 from Gallaecio/master

Regenerated PO file and updated Galician translation
French translation update + several fixes from review.
Fixed a typo leading to a neverding animation where it should have been played only once.
Added diagonal check before pushing stones or dealing with shrooms.

I wanted to test this on scripting level, so I added a new If Event,
checking a function return value and starting a second event
accordingly.

I also made the engine tell when an event id is invalid.
Added thunder in the path3 map and other tweaks.

- Fixed a crash when quitting the game in the rain scene as a sound was loaded
  but never registered.
- Tweaked ripples speed.
- Reduced the rain particle cap a lot to help fps with this particle effect.
Kept on working on the path3 elbrus map.

- Added all the props
- Worked on gates and adapted the corresponding tilesets slightly toward this.
- Added the first dialogue.

This map not far from being finished :)
Changed Orlinn's portrait a bit.

Made him less pale and made his head shape more oval.
Started working on the path3 miniboss.

- Added the eyeball map and battle enemy.
- Added support for custom enemy respawn time.
- Simplified the LICENSES file while seeing it.
- Made the cemetery gates close as a start for sandboxing it.
Started working on the path3 mini-boss.

That one is going to be a bit twisted ;)
- Added the Harlequin sprite and related event in the path3 map.
Added most of the path3 miniboss core mechanisms. I'll add the rest later.
Increased the harlequin sprite size a bit in its stamina icon.
Added missing skills for the mini-boss fight.
Added support to disable an enemy zone at the script level.
Basically finished the path3 map.
Fixed a memleak while seeing it.
Polished a bit the monster AI decision default algorithm.

- Added party target support that was always there in fact.
- Made it not crush the all_actors deques when taking a target.
- Made it check for the necessary skill points before using a skill.
- Remove useless dead code.
Dropped c++ based lightning support.

Since I could do better with a few lines in a script, I don't see the need to keep
such a complicated piece that was also dragging down the map loading time.
Fixed attack points for Lord Banesore and the Eyeball monsters.
Removed an not existing event link.