Use Network name if there is one when creating new bnc-enabled network.

[tralves]

Problem:
When creating a new network with bouncer, the bouncer provider would always replace the network name with Network1, Network2, etc.

We may want to provide a better network name. E.g., when creating an IRC.com network in the app.

Solution:
With this PR, the BouncerProvider will give priority to the network name, if it exists, while making sure the network name is unique (as it used to).
For example, if the new network name is MyNetwork, the BouncerProvider will try the names MyNetwork, MyNetwork2, MyNetwork3, etc.
If the network name is not set, the BouncerProvider will behave as preciously and try assigning the names Network1, Network2, Network3, etc.