refactor: Move functions that lookup asset ids from task inventory or pass them through to ScriptUtils class in OpenSim.Region.Framework.dll

Renames functions to better reflect what they do.
This is so that code registering with modInvoke() can reuse this code to provide functions that behave in a consistent manner with existing LSL/OSSL functions.
Merge branch 'master' of ssh://opensimulator.org/var/git/opensim