Allow usage of a Google Maps API KEY with BaseGMapWidget

[victor-o-silva]

Since June 2016, Google Maps API requires an API Key, otherwise the maps may fail to load:

This PR gives developers the ability to supply their API Keys to the Google Maps API by setting the attribute google_maps_api_key in BaseGMapWidget subclasses:

class GMapPolygonWidget(forms.gis.BaseGMapWidget, forms.gis.PolygonWidget):
    google_maps_api_key = 'YOUR-GOOGLE-MAPS-API-KEY-HERE'

Changes

floppyforms/gis/widgets.py

• Made the form's media dynamic by defining it as a property instead of a static class
• Stopped the escaping of ampersands in the gmaps script url, for it was being rendered like this: (...)js?v=3&sensor=false
• Removed sensor parameter, for it's no longer required
• Appended key parameter if API Key is set

docs/geodjango.rst

• To keep the docs simple, used BaseOsmWidget instead of BaseGMapWidget in most examples, because BaseGMapWidget now requires a special attribute
• Documented BaseGMapWidget.google_maps_api_key and put a link to where developers can obtain the Google Maps API Key
• Fixed a minor typo

[victor-o-silva]

Travis failed before the tests even started:

mv: cannot stat `/etc/apt/sources.list.d/pgdg-source.list': No such file or directory The command "sudo mv /etc/apt/sources.list.d/pgdg-source.list /tmp" failed and exited with 1

[gregmuellegger]

That is great work! Thanks for the investigation and PR. I'll test the changes locally and will then get it merged and released.

[gregmuellegger]

Merged and released as 1.7.0: https://pypi.python.org/pypi/django-floppyforms