Modify how we use urlencode as a filter to account for double encoding with PIC

[reginafcompton]

Two things

Look at the filter here: https://github.com/datamade/django-councilmatic/blob/master/councilmatic_core/templates/councilmatic_core/legislation.html#L372

Add an explanatory note here: https://github.com/datamade/django-councilmatic/blob/master/councilmatic_core/models.py#L336

-OR-

We might think about how to standard full_text_doc_url for all Councilmatics, rather than expecting the city-specific Councilmatic to customize this. @fgregg, thoughts?

[fgregg]

seems like a standard full_text_doc_url would be the way to go, particularly since the PIC url should be moved to settings variable

[reginafcompton]

It looks like this model property varies among the Councilmatics (e.g., Chicago renders a PDF, but NYC does not). It seems like it would be best to allow for this type of flexibility and, instead, make the updates to Chicago and LA Metro, which need the double URL encoding.

https://github.com/datamade/django-councilmatic/blob/master/councilmatic_core/models.py#L336