constraints: add test for adding a uniqueness constraint
constraints: add uniqueness constraint implementation
constraints: make bindAllTo recursive
constraints: hook constraints.js into core
constraints: remove function filter from bindAllTo
add entire exception body to error object. closes #129
attach cause to exception, if one exists
constraints: add test checking if uniqueness constraints are effective
constraints: add test for retrieving a uniqueness constraint
constraints: add implementation for retrieving a uniqueness constraint
constraints: fix retrieval test
constraints: add test for retrieving all uniqueness constraints
constraints: add test for retrieving a specific uniqueness constraint
constraints: implement list all functionality for uniqueness constraints
constraints: implement test for dropping a uniqueness constraint
constraints: drop uniqueness constraint
constraints: fix drop uniqueness constraint test
constraints: add test for listing constraints for a label
constraints: list constraints for a label
constraints: add test for listing all constraints