Separated tiles used for defining common actions from the ones used to see enemies positions.

This is fixing #214 to me.

Now workers are much more efficient while creatures won't know of each others
until they face one another.

There is another bug you can see in Scream in the Dark though.
The AI being on the right of the map have worker that don't do anything.
As far as I've looked, it's because they are trying to reach undiggable tiles on the right.

I'll fix this in another commit.
Fixed computation of reachable diggable tiles and claimable walls.

This half fixes the way the creature AI to the right of The scream in the dark map
is acting.
The next bug is linked to diggable tiles being accross water. I'll have a look
at it in the next commit.
Made sure water (and lava) paths were taken in account correctly.
Hopefully fixed compilation on Linux...

... while not breaking it on Windows. :)
Updated the readme's files list and descriptions.
Fixed the crash happening when cancelling the Ogre config dialog.

Fixes #272
Merge pull request #281 from Bertram25/development

Improved the way creatures see and seek claimable and diggable tiles.