New ExecutableBlocks supports variables ! (Variables are linked to the block)

New the block title supports the variables placeholders but also the placeholder %usage%

Fix the usage is now save correctly, before it was reset if the server was turned off.

Improve the performances of the plugins (EI - EB).
especially for the code of:
- the LOOP activator
- the management of the custom placeholders
- the updates of holograms (EB, block titles)