cli: use pools implied VRF per default

If no VRF is explicitly specified, use the implied VRF of the pool.

Fixes #662.
cli: add option to add hosts to network

This allows the user to add hosts in to a new network when assigning from a
pool or other prefix.

For example, we have pool 'core-links' containing IPv4 and IPv6 networks. Now
we want to grab a new link network and we can do that for both IPv4 and IPv6
and adding hosts in each with the command:

kll@lingloi320 ~ $ nipap address add from-pool core-links family dual-stack description "my link" add-hosts foo-core-1,bar-core-1
Network 1.3.3.20/31 added to VRF 'default' [RT: -]: my link
Host 1.3.3.20/31 added to VRF 'default' [RT: -]: foo-core-1
Host 1.3.3.21/31 added to VRF 'default' [RT: -]: bar-core-1
Network 2a00:800:0:2::5:0/112 added to VRF 'default' [RT: -]: my link
Host 2a00:800:0:2::5:1/112 added to VRF 'default' [RT: -]: foo-core-1
Host 2a00:800:0:2::5:2/112 added to VRF 'default' [RT: -]: bar-core-1
kll@lingloi320 ~ $ nipap address list 1.3.3.20/31
Searching for prefixes in any VRF...
VRF            Prefix                           #  Node                Order          Customer       Description
================================================================================================================
-              1.3.3.0/24                     R -  None                None           None           Core Link networks
-                1.3.3.20/31                  A -  None                None           None           my link
-                  1.3.3.20/31                H -  foo-core-1          None           None           None
-                  1.3.3.21/31                H -  bar-core-1          None           None           None

The output of the add command has changed somewhat and it is now printed
if the new prefix is a host or network.

Fixes #661.
Merge pull request #663 from plajjan/661-cli-add-hosts

cli: add option to add hosts to network
www: AngularJS implementation of VRF list

Created AngularJS template for the VRF list page and added a route to it.

Fixes #641
www: AngularJS implementation of pool list

Created AngularJS template for the pool list page and added a route to
it.

Fixes #642
Merge pull request #665 from garberg/642-angularify_pool_list

www: AngularJS implementation of pool list
Merge pull request #666 from garberg/641-angualrify_vrf_list

www: AngularJS implementation of VRF list
backend: fix order of operation around forking

The backend class initiates the database connection in __init__ so
initing the backend class before we fork means the backend processes
will have one shared socket (sockets are shared across the processes)
between all the backend workers. This obviously isn't a good thing since
we need at least one database connection per backend to achieve some
parallelism. I'm sure there are other peculiarities that would steam
from sharing database connection.

By simply moving the init of the backend class to after the fork we
improve on this code. Still seeing weird issues on certain machines so
the forking code definitely isn't complete but it's getting there.
Update NEWS file for v0.27.2

and bump version numbers..