[nemo-qml-plugin-connectivity] Implement invokable function

The previous commit removed the implementation of a public symbol
which is called by code internally in the implementation, which
subsequently crashed.

This commit adds an empty implementation for the function as a
temporary workaround.
Merge pull request #5 from chriadam/crashfix

[nemo-qml-plugin-connectivity] Implement invokable function
Bump version
[nemo-qml-plugin-connectivity]  send signals whenever state changes.

Some clients are monitoring the state not just when they try
for a connection.