Fixed a bug in GridWorldMap World2Index function.

There was a rounding error when the world coordinate was
in the X.0 - X.499.. range.

In that case (x - 0.5) sholud be rounded to the nearest integer
and not to the floor integer.
Removed some Debug.Log junk I forgot to remove before.
First implementation of the Drop action.

The action Drop is used to unload the bot of the gold it's carrying.

The gold can be dropped only in the spawn area.

The spawn area is the area where the bot spawn the first time.
New ManualControl to control the Bot by Keyboard.

Space for "grab" and Shift for "drop".
Bot prefab updated.
Merge branch 'gold_store' into develop