Add TransparentBsdfNode
CCycles: Add Separate HSV
CSycles: Add Separate HSV node
Add support for exporting Separate HSV Node.

Resolves #23
together with commits
159cdfae8db90d9db39aa6a0230b131b875198d7 and
52e096def7b936792064508b869028585c9126ad
CCycles: Add support for Separate RGB node.

partly resolves #25
CSycles: Add Separate RGB Node

Partly resolves #25
exporter: Add support for Separate RGB node.

Finally resolves #25
Outputs were wrongly name.
Input and outputs had wrong internal names.
Proper template function implementation of get_ccimage.
Nesting groups with inputs directly connected caused stack overflow.

Fixes #22
Use value from group input socket if it isn't connected.

Partly resolves #27
Ensure value of input socket on group is used if no incoming link is found.

Resolves #27
Output node was accidently being skipped resulting in non-functional exported code.
Small clean-ups.
Prune node and link list before generating code.

Resolves #29