Expand beforeInit event to allow halting of init event

[Caleb Troughton]

Folks need to ensure some things happen beforeInit, while transforming the deck in some way during beforeInit. Some of those things are async so init gets fired before they're ready. This is the remedy:

• beforeInit event gets two new methods, lockInit and releaseInit.
• Calling lockInit will prevent the init event from firing until releaseInit is called on the same event.
• Firing of init will wait until all locks are released.
• There will be a timeout limit for locks, with warning or error if that time limit is reached.

[Caleb Troughton]

@twitwi This is in master now. Would love for you to try it out. The interface is as described in the ticket. Default timeout for lock release is 10 seconds.

[Rémi Emonet]

@imakewebthings Very good. I could try and it seems to be working well with my extensions. I only had to also fill the slide array before calling the preinit (as the extensions are relying on it to be filled). See #156

This reminded me of my very old pull request #80 (error 500 on github for me :( )

[Caleb Troughton]

This is included in the 1.1.0 release.

[Rémi Emonet]

Thanks.