Added django-dajaxice and select2 to support autocompletion

tnc-ba/strongTNC#28
Added module that provides global non-model-bound permissions

The approach is based on the stackoverflow answer at
http://stackoverflow.com/a/13952198/284318.
Changed setpassword command to create both readonly and read-write users

Extended setpassword management command with two new features:

- Command now creates both readonly user and admin user
- The admin user now receives the `write_access` permission
Implemented login with two different users

The user can now choose in the login form whether he wants to login as
readonly user or as read/write user.
Fixed broken regular expressions in urls.py

The URL definitions in `tncapp/urls.py` contained some broken regular
expressions (missing trailing slash). This commit fixes these.
Check permissions in backend

Added `@permission_required` checks in all relevant views.

There is now a new test function in `tests/test_auth.py` that verifies
permissions on all the relevant URLs. If new create/update/delete URLs
are added, the test parameters should be adjusted accordingly.
Check permissions in frontend

Form fields are disabled using the new `{% input_editability %}`
template tag.

Other blocks are checked using the following `if`-statement:

    {% if 'tncapp.write_access' in perms %}

PS: Yes, `editability` *is* a word! https://en.wiktionary.org/wiki/editability
Added ConfigParser to settings.ini
Added settings.sample.ini
Updated Travis CI config

With the new split config file we need an additional configuration step
in .travis.yml.
Added TIME_ZONE to settings.ini

Refs tnc-ba/strongTNC#94.
Added new swid app and models

- New django app in `apps/swid`
- Model definitions in `models.py`
- Admin configuration in `admin.py`
Updated models according to current schema

- Compared models with SQL schema in strongSwan sourcecode
- Made changes to be compatible with that reference schema

The goal is that the schema can be generated by django in the future.
The main advantage of that is that we can generate the schema for
different database backends.
Added django-admin configuration file

It is now possible to view, add and edit data from all tables using the
django admin interface.
Created SWID-XML processing function

This adds `lxml` as a new requirement. In contrast to Python's built-in
XML parsers, it's much faster and also provides SAX like parsers that
don't load the entire tag into memory.

The commit also adds .swidtag files for testing purposes.
Added ajax autocomplete for the directories dropdown in the policy view

tnc-ba/strongTNC#134
Added function to import SWID tags from the workitems result field in the DB

Also, there is now a manage.py command to import swid tags from file
(tnc-ba/strongTNC#133)
Added trusted flag to device
Removed os.path.join to ensure windows compatibility
Configured urls for swid app