Bug 929718 - Fix duplicate countries and cities in API

Because the custom manager that implements field-specific privacy
requires us to include privacy_country or privacy_city in the values()
part of the query, there's not a good way to fix this in the
query itself.

Added some code that fixes up the result list after the query
to collapse the duplicates down again and add up the population.
Merge pull request #682 from dpoirier/bug-929718-countries-api-duplicates

Bug 929718 - Fix duplicate countries and cities in API
[Fix 936390] Add space after '!' in e-mail invitation string.
Merge pull request #715 from sunu/936390

[Fix 936390] Add space after '!' in e-mail invitation string.
Bug 877315 - count vouched members in admin

In the admin list for groups, add a column to display the number of
vouched members, similar to the current column that counts all
members.

This implementation relies on the database implementing Booleans
as integers, so we can Sum() them. It works for MySQL, which is
how Mozillians is currently deployed.

A test is added that will fail if we ever try to use Mozillians
with a database where this doesn't work, which will alert us to
find another approach.
Merge pull request #708 from dpoirier/bug-877315-count-vouched-members

Bug 877315 - count vouched members in admin
[fix bug 934495] Move messages block inside content_wrapper.
[fix bug 932987] Move templates to 'mozillians' app root.
[fix bug 938037] Fix image path in 500.html.
Merge pull request #718 from glogiotatidis/500error

[fix bug 938037] Fix image path in 500.html.