Version 0.6.0

Changed the concept of primarily recording PDS-like "products" in the database and data structures, and changed the concept to capture "records" of various kinds (ImageRecords, LightRecords, and derived things like PanoRecords) in the database and as the primary data unit for use and interaction. And then PDS "products" will be made at a later time via a process that sources one or many records.

Added

• image_records.py (this replaces the concept of raw_products.py)
• create_image.py (this replaces most of the functionality of the previous create_raw.py)
• image_tags.py which contains image tag information.
• image_requests.py defines the table for holding image requests.
• Junction tables to connect LDST information to ImageRequests and ImageTags to ImageRecords.
• ldst.py table which contains LDST information.
• light_records.py which handles information about luminaire state.
• anaglyph.py
• pano_check.py to sort through image records and figure out what would be a good panorama set.

Changed

• header.pga_gain_dict structure now has values that are always floats, which helps to determine whether this transformation needs to be applied.
• image_stats.py is the new raw_stats.py, supporting ImageRecord objects.
• pano_products.py is now pano_records.py, supporting ImageRecord objects.
• create_pano.py now supports ImageRecords and PanoRecords.
• create_raw.py rearchitected to gather information from "records" to build XML PDS labels.
• create_vis_dbs entry point changed to vis_create_dbs to conform with other vis-related entry points.
• pid.VISID now properly sorts the uncompressed "z" state lower (better) than the lossless compressed "a" state.
• pid.VISID now has a best_compression() function to sort out the best compression state
  from an iterable containing may compression states from a single observation.