[Engine] Initial implemention of Smuxi hooks (closes: #125)

Supported hook points:
 * protocol-manager/on-connected
 * protocol-manager/on-disconnected
 * protocol-manager/on-message-sent
 * protocol-manager/on-message-received

Supported hook commands:
 * Session.Command
 * ProtocolManager.Command
Switched submodules from qNETp to GitHub

git.qnetp.net stays as official mirror
Merge branch 'stable'