Join Targets: Add Category

[raprasad]

For the "JoinTarget" model, add a Category field.

• Category field
  • May be stored in the models.py file. (e.g. list of pairs, etc)
  • Example:

from django.utils.text import slugify

CATEGORIES = ('Census Tract', 'Census Block', 'Census Block Group', ...)
CATEGORY_CHOICES = [ (slugify(x.upper()), x) for x in CATEGORIES]

class JoinTarget(models.Model):
    ...
    category = models.CharField(max_length=100, choices=CATEGORY_CHOICES)

Categories should be standard geospatial identifiers and preferably have a format that may be machine-validated. (e.g. A Census Tract is 6 digits--zero-padded, etc.)

• Are there are already standard types in GeoNode 2.x?