[WFCORE-457] Attribute groups -- the basics
[WFCORE-457] Attribute groups -- xml persistence
[WFCORE-457] Attribute groups -- reflect in sorting of read-resource-description and read-operation-description output
[WFCORE-457] Attribute groups -- sort attributes in read-resource responses by group and then by name
Merge pull request #391 from bstansberry/attr-group

[WFCORE-457] Attribute group basics