Allow different pv naming convensions as input options

[evalott100]

In #42

All attribute names were converted to pascal case. We should add a new options enum to pass into the ioc specifying what conversion to do, and specifying the epics seperator.

[GDYendell]

I am happy with what you have on your branch so far, but would like either

• sub controller node and leaf naming conventions to specified separately (e.g. caps for nodes and pascal for leaf)
• don't convert node names at all and just use the string passed to register_sub_controller - we only need to convert the attribute names really as they have to be defined as python attribute names