-added variables-based pruning to resource iteration, *large* effect on performance
-created a 'ResourceWrapper' base class and added to resources.py
-added fix for rez-1 'version as a float' bug
-added grafting of changelog to Packages
-added grafting of other release info (revision etc) to Packages
-added ResourceNotFound exception, so Packages no longer accidentally
mask resource metadata bugs
-fixed bug in WithDataAccessors not taking into account attributes in base classes
-added new 'rez-search' tool, for finding packages and package-like resources
-various bugfixes wrt package resources
- WIP, more package-related code porting to be done.