Mostly GUI Bugfixes

[MJWeberg]

Assorted bugfixes, mostly to GUI tools:

• Fixed and expanded support in read_cube() for EIS rasters containing multiple exposures per slit position (this type of observation is very rare)
• eis_explore_raster
  • Added support for multi-exposure files
  • Added Chainti reference line for Fe IX at 188.493 Angstroms
  • Fixed issue where selections on the spectrum plots were being incorrectly reset when loading a new file
• eis_catalog
  • Added some logic to the database search to prevent incorrect study information from being returned when the tl_id is broken (current DB issue has been fixed, but this will help if there is ever a new problem)
  • Fixed crash on some systems when selecting the "Image" tab before selecting an observation from the list