'nipap address view' now shows correct prefix

Fixes an issue with the 'nipap address view' CLI command did not show
the correct prefix if used on a host prefix with other host prefixes
before it in the assignment.

Fixes #414
Simplify the logic around parents/children_depth

This makes the code a bit more compact and easier to read plus that we
explicitly check for -1 instead of allowing any negative value.
Merge pull request #415 from garberg/fix_address_view

'nipap address view' now shows correct prefix
Merge pull request #417 from plajjan/parent-children-depth-logic

Simplify the logic around parents/children_depth
Update upgrade file from db ver 1 to 2

Also allow the creation of debrepo even when not on gh-pages branch.
Update last_modified timestamp on db updates

Any update to the ip_net_plan table will now update the timestamp of the
prefix being updated.

Part of #367.
Improve wording and update db version number

The wording for the questions asked to the user have been reworded
somewhat.

Database structure number in nipapd.config is updated to the latest (2).

Part of #367.
Add new timestamp values to prefixes

The backend now serves two new values, the 'added' and 'last_modified'
columns of the database which are the respective timestamps for when a
prefix was first added and last modified. Both values are also
searchable via the prefix smart search function. Neither value is
writable as the backend updates them automatically.

xmlrpclib, both in the backend and in pynipap, is used with
use_datetime=True which means that the timestamps will automatically be
converted into datetime objects for easier use.

Pynipap does naturally not support saving the values as they are
read-only. The CLI will show the 'added' and 'last_modified' timestamps
when viewing a prefix. At this time, they are mostly meant for internal
usage or via the API, e.g. to bring up all prefixes that have been
changed the last hour to sync with another system.

Fixes #367.
Reverse previous accidental commit

This is reversal of some code that was mistakenly commited together with
a bunch of other code.
Add children column

The children column will be used to cache the number of direct
sub-prefixes (children) to a prefix. It is used by the web front-end to
determine if a expand/collapse icon should be shown or not.

Part of #421.
Fix unit test for added/last_modified timestamps

Part of #367
Update changelogs for v0.22.0
Remove rename of trigger function

This was a half-baked changed that got accidentally commited. Removing
it!
Remove SQL functions on clean
Fix column name in upgrade file

Part of #421
Remove old function

Function has been removed.. so we remove the old one.
Add pynipap to dependencies of nipap-cli

I was under the impression that a) pynipap was a dependency of nipap-cli
already and b) that it was calculated from the setup.py file. Apparently
not though, so here goes.

Fixes #420.
Small fix to release-handling doc
Fix dependency type

pynipap -> python-pynipap

Fixes of #420
Update release handling document