Implemented Handle and Template modifier. Cleanup uf doc.
Merge branch 'master' of github.com:tec/migration

Conflicts:
	src/migration/mapping_test.go
Revert "New Mapping rules that insert context information into atrributes, e.g.:"

This reverts commit a68a5870550be840ca0e0963a19f54e62787a3dc.

Conflicts:
	src/migration/mapping_test.go