Uni-directional signatures may omit scores: the four add*SignatureSet() functions no longer require a non-empty score, which is stored as NULL and comes back as NA. addSignature() now rolls back and errors if the feature step stored no rows, instead of returning a signature id for an empty signature. Needs OmicSignature >= 1.4.1, which keeps NA-score rows (#258, montilab/SigRepo_Server#89).
addUser() and updateUser() now grant privileges on the database the connection is on instead of a hard-coded sigrepo schema, and checkDBTable() reads SHOW TABLES by position, so seeding and lookups work on a database with any name (#245, montilab/SigRepo_Server#130).
