Replace inputId by an input in UniversalInput

[bassetmatt]

In the file src/game/entity/dev/controllable.cpp, there are cases in a switch on the variable actionId from the field Keybind::action.inputId, and these cases are used on this variable but aren't really explicit:

• case 0
• case 1
• case 2
• case 3
• case 6

These constants could be less obscure if they were replaced by members of an enum with self-explanatory names.

[gbrivady]

To give more insight: actions are intended to have stuff such as UNIVERSAL_UP, UNIVERSAL_DOWN, ... , SPECIAL_ACTION_1 etc, but since I did not know how many were needed, I wanted to wait for version 0.2 and the combat to fix stuff. So will be adressed in next update

Edit : see the struct UniversalInput within engine/input/input_handler.h. The member int actionId is the thing to edit.