interface improvements for creating measures and interacting with tables

* Make it possible to define quanta with a string macro
* Custom type for handling measurement sets
* Custom types for the various kinds of measures
* Implement get/put methods for data, model data, and corrected cols
* Methods for adding and removing rows/columns from tables
* Define a basic test for tables manipulation
Merge pull request #2 from mweastwood/improvements

interface improvements for creating measures and interacting with tables