Blender Git Loki

First stages of easier "expressions" creation...

It is now possible to create "scripted expression" drivers by simply
clicking on some property, and typing some short Python expression
prefixed with a '#'. This will result in a scripted expression driver,
with the typed-in text being created.

For example, you can click on X-Location of the default cube, and
type:
#sin(frame)
and a new driver will be created for the x-location of the cube. This
will use the current frame value, and modulate this with a sine wave.

Do note though, that the current frame is a special case here. In the
current implementation, a special "frame" driver variable, which
references the current scene frame is created automatically, so that
this simple and (assumed) common case will work straight out of the
box.

Future improvements:
- Explore possibilities of semi-automated extraction of variables from
such expressions, resulting in automated variable extraction. (Doing
away with variables completely is definitely 100% off the agenda
though)
- Look into some ways of defining some shorthands for referencing
local data (possibly related to variable extraction?)