Add related task action to filter api

@twinge Can you review

I removed the "Related Task" filter from filtering on the front end and moved it to part of the contacts filter on the backend.  There was an issue reported with the request url getting too long when filtering by related task.
==


On Wed, Aug 6, 2014 at 9:05 AM, adammeyer <notifications@github.com> wrote:

> In app/models/contact_filter.rb:
>
> > @@ -120,6 +120,18 @@ def filter(contacts)
> >          filtered_contacts = filtered_contacts.where('contacts.timezone' => @filters[:timezone])
> >        end
> >
> > +      if @filters[:relatedTaskAction].present? && @filters[:relatedTaskAction].first != ''
> > +        if @filters[:relatedTaskAction].first === 'null'
>
> The === is invalid, I'm not sure what to use instead.
>
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> <https://github.com/CruGlobal/mpdx/pull/100/files#r15871487>.
>