FromHoudiniGroupConverter ignores internal groups.

This fixes a bug where the group converter would take preference just because of the selection state. I've verified the fix, but unfortunately I can't write a test case, because there doesn't appear to be any way to create internal groups from python...
Connecting indirect inputs for subnets

When expanding OBJ_SceneCacheTransforms, the child nodes will be connected to the subnet indirect input.
Auto-layout of expanded nodes
File parms channel reference their parent
SOP and Geo Path parms channel reference their parent
fixed crash in SOP info text
Adding interruptors for SceneCache nodes.

Expanding an OBJ_SceneCacheTransform and cooking a SOP_SceneCacheSource can now be interrupted using the escape key.
Update TypeIds.h

Range 111000-111999 clashes with existing range for IECoreHoudini
Updated IECore/TypeIds.h to reflect rejig of Arnold and Houdini TypeIds.
Merge pull request #82 from johnhaddon/dmar-fix-arnold-typeids

Dmar fix arnold typeids
correctly ignoring internal groups
Merge pull request #77 from andrewkaufman/convertSelectionBug

FromHoudiniGroupConverter ignores internal groups
Merge pull request #80 from andrewkaufman/expandImprovements

Improvements for expanding SceneCaches in Houdini