Label visibility default values

[kylecombes]

Current behavior

• When a label defaults to visible, default: "True" (string)
• When a label defaults to invisible, default is undefined

Desired behavior

• When a label defaults to visible, visible: true (boolean)
• When a label defaults to invisible, visible: false

[newsch]

Neat! This was a three-part bug:

• the default field for labels wasn't set as required
• the mongo_to_dict function was returning strings of BooleanFields
• the mongo_to_dict function wasn't checking to see if fields existed in dictionary correctly - checking obj[field_name] rather than field_name in obj, so if the value of obj[field_name] was False the check for the field returned False