FungusScript can now be made into a prefab (see notes!)

All sequence and command components are now added to the main
FungusScript object. This change enables you to make a prefab out of
any FungusScript. FungusScript prefabs can now be edited using the
Fungus Script window. You still need to instantiate a Fungus Script
prefab in order to run it.
Fixed Sfxr borking the popup editor style
Can now make prefabs from legacy FungusScripts

If you have a FungusScript from an earlier beta release that has child
Sequence objects, you can now make a prefab from that FungusScript.
Create Sequence adds to right side of selected Sequence
Position new sequence nodes in centre of script view
Click outside node to deselect
Changed sequence node style (smaller and stands out more)
Fixed adding new commands to legacy sequence objects
Hide script field for commands in inspector.

This fixes an issue where the user could change the type of script
being used for a command which would trigger a bunch of null exception
errors (because the commandList might now contain a null entry).
Merge remote-tracking branch 'source/master' into develop