[EastSussex] tweaks after comments from ESCC

 - change front-page text
 - rename Category to Type
    By overriding report/new/category template snippet.  This is hacked
    in (including substitution of the "-- Pick a category --" text, as
    not sure how to simply do this as a cobrand-specific translation.
 - hide footer on mobile view
 - pothole field input and display
      This is a temporary request, which we hope will be superseded by
    full integration in due course.
      A command is documented in the cobrand to set the "extra" on the
    contact info for the Potholes category.  This is then displayed by
    the UI.  The default process_extras places it in extra, for
    potential future processing.
      As this is a temporary fix, we are calling this field
    "detail_size", as this is automatically included in "Details" and
    therefore also sent in the email.
      (This means that we may need to update data later on to call this
    "pothole_size" or similar in future?)
 - contrast tweaks (Via request from Matt Tooke at ESCC.)
   Not all handled precisely as he suggests:
    * spacing of button nav -- more or less as suggested, but tweaks for
    the <span> selected button, and reduced padding on non-frontpage.
    * sign-in buttons: fixed using CSS for .green-btn instead of adding
    HTML class throughout.
    * mobile-footer: edited <footer> css, as suggested by Dave Arter.
 - revert problematic CSS (breaks map report page)
 - Remove spurious "FixMyStreet" button
 - frontpage subheading wording
Let cobrand override geocoder

Fixing issues with Bing geocoding for East Sussex,
for example "Church Street".