Convention was not to but after discussion on 918941483f
we agree its
best to change the convention.
Names now mostly follow RNA.
Some exceptions:
- Use 'nodetrees' instead of 'nodegroups'
since the struct is called NodeTree.
- Use 'gpencils' instead of 'grease_pencil'
since 'gpencil' is a common abbreviation in the C code.
Other exceptions:
- Leave 'wm' as it's a list of one.
- Leave 'ipo' as is for versioning.