Customizations to Django's template error handling

* TypeError - it is possible that TypeError is triggered not by missing variable in template or missing arguments of the function used in template, but inside th

* regarding: https://bitbucket.org/vanschelven/django/commits/10e5d98a776c - we decided not to change that to keep changes to Django to
minimum. The error message is still readable and we should not have a problem with understanding the error once it will end up
in sentry.

https://bitbucket.org/vanschelven/online_apps/issue/611 is related.

448015ccd74f35d47e5e6c30e642f82acbc653a and 90043f9a1b3a0ef846a91dabeb6c21b559d75d0e made these customizations earlier,
but they were undone in the upgrade to Django 1.6.