Seek() should also reset all controllers

[jeroenwalter]

Seek() is implemented as a replay of all the midi messages from the start, while muting any note on/off requests. This allows for control changes and tempo changes to be done correctly.
It also mutes all channels before the replay.
However, it doesn't reset all controllers before the replay, so controllers like modulation and pitch will still have their last value.

When the player starts a new song, all controllers are reset. As the Seek operation basically is the same as starting a new song, it should also reset all controllers.