application: Remove unused variable
tox: Fix mistake when creating a new contact

We need to pass the binary key to neuland_contact_new(), not the hex
string.
chat widget: Add neuland_chat_widget_get_contact()
window: Accept and Discard buttons for requests

These show up in the right header bar when the contact's friend request
has not been accepted yet. Still work in progress.
window: Remove debug message
contact: Allow setting name to NULL
window: Set title to Tox ID when name == NULL
contact: Add get and set functions for number prop
Implement accepting contact requests, BFCC! [0]

Receiving and accepting Tox friend requests is working now.

[0] BFCC: Big Fat Chaos Commit!