Fix inconsistent guide_objects returned by various search methods

The agActor has three different methods for getting the guide objects and they currently return a slightly different mix of return types, e.g. a numpy array, structured numpy array, and an astropy table. 

The astropy table (returned by the gaia catalog search method) is converted into a structured array properly.  The query from the design_id alone returns a non-structured numpy array, which should be made consistent.