Scripted plugins (v0.9)

[Charlie Brej]

I think the scripted plugin is now pretty much complete. I had a go at 
recreating the fade-in and spinfinity plugins using the scripting system as well 
as a couple others. On the whole, it is all rather easy and I haven't yet seen 
any major pitfalls.

The code is living in the "scripted-plugin" branch and there is an example 
plugin and theme, both called (highly imaginatively) "script". The scripts 
themselves are reasonably self explanatory [1]. I will make a short list of 
provided functions soon.

If anyone has a few minutes to take a look then please try it and see if you can 
make some changes to the script without it barfing.

[1] 
http://cgit.freedesktop.org/plymouth/tree/themes/script/script.script?h=scripted-plugin