Added gl:primitive:selectable flag
Added workaround for 3delight 11.0 in IECoreRI::Renderer::worldEnd.

3delight 11.0.0 now generates a new RtContextHandle in worldEnd and whisks the other one away onto a background thread to do rerendering, so we have to talk to the new one instead. New approach tests OK in 11.0.0 and 10.0.173. Note that one test (light edits) is still failing in 11.0.0, but this so far at least appears unrelated to the context changes.
Adjusting SceneCache read time in Houdini.

We need to adjust the time we read SceneCaches inside Houdini because Houdini treats time starting at Frame 1, while SceneInterfaces treat time starting at Frame 0. Note that we should really be adjusting time by 1/fps used at cache time, but we don't have access to that, so we currently assume that Houdini's current frame rate is representative.
HoudiniScene uses SceneInterface standards for time.

Calls to HoudiniScene will expect SceneInterface time (starting from Frame 0), and will internally adjust when querying Houdini.
SceneCache ROP adjusts time before querying HoudiniScene
Correcting HoudiniScene customAttributeReaders so the ReadFn accounts for time.

Now all links written from Houdini are time re-mapped.
Merge pull request #130 from danieldresser/drawSelectedFlag

Added gl:primitive:selectable flag
Merge pull request #131 from johnhaddon/delight11Fixes

Added workaround for 3delight 11.0 in IECoreRI::Renderer::worldEnd.
defaultTime is now private and renamed to adjustedDefaultTime
Merge pull request #132 from andrewkaufman/timeOffset

Fixing SceneInterface Time in Houdini