Database schema updates

This releases introduces some updates that slightly change the acsql database schema, namely:

1. Column names that had hyphens in them have been changed to underscores as to simplify queries through python and sqlalchemy.
2. Precision for float datatypes has been increased. Now values for columns such as expstart will contain the full precision as found in the headers.
3. The path column in the master table now only stores the path to the rootname within the filesystem, not an absolute path. This helps to avoid exposing internal directory structure in the database.