First check in of gui mods
 Commit of first mods in my development branch for the GUI
Changed code to display N/A instead of -1 for unsaved versions of datasets
- Remove <variable> elements for excluded variables (per-variable catalogs)
initial support for comments
Initial changes to support comments
Finished adding support for comments written into the db.
Added more support for comments, this time in the dataset description panel
Slight mod to the editor dialog
added the help file for html based information
added code to support new commands
- For CMIP5, invalid characters in DRS fields are mapped to a dash (-).
- Updated default model ID table
- Validate DRS fields after all context values are set.
- Cleaned up docstrings
 modifications to better support versioning
Removed some redundant code and cleaned up some unnecessary code related to versioning
added support to delete datasets and cleaned up some code
- Trap missing coordinate values
- Trap coordinate ranges longer than 32 chars
- V2.7.5
- Catches the error when a coordinate variable has missing data.