Blender Git Loki

Type change in the group socket update function.

In group node and group input/output updates:
Instead of discarding group sockts with a type mismatch (which breaks
any link), keep the socket and update its type.
This can require a subsequent node tree link update to check for invalid
socket connections. Links should be flagged as invalid and ignored by
node systems, rather than removed outright.

Note that the nodeModifySocketType function only works with static
socket types currently and does not fully support custom socket types
(e.g. sockets defined in python). Any group interface with a custom type
will generate a generic SOCK_CUSTOM socket. This should be addressed
soon by making nodeModifySocketType work with idnames rather than
integer types.