Initial pass at Sign display
Initial Signs template
Add lazy backref to Sign relations
Adding some repr methods
Sign / CDP relationship changes

CDP and Sign table names have now been swapped:
    Sign is the canonical list of CDP signs
    CDP holds all variations upon that sign
Relns between CDP and Sign, Description, ORACC, CDLI renamed
Fix CDP model repr
Second pass at Sign and CDP records views
Rename SQL dump to save space
Updated SQL dump to 22nd of May
Fix spacing in views
More sensible CDP relationship names
Better display of CDP record details
Allow Cdp Description, ORACC, CDLI cols to be nullable
Add Notebook for CDP import

This will import the CSV into Pandas, clean it up,
then populate Sign, ORACC, CDLI, and Description tables, before
populating the CDP table

Also deals with horrible notnull() gotcha which drops "NA" strings
Adding DB dumps