Room: replace metaInformationForLocating with a foreign-key to a RoomTag

[Luke Faraone]

A string is really hard to query, so instead we should just do a ManyToMany field against an (as of yet nonextant) model for a RoomTag.

Suggested model code:

class RoomTagType(models.Model):
    name = models.CharField(max_length)

class RoomTag(models.Model):
    name = models.CharField(max_length)
    type = models.ForeignKey(RoomTagType)