[Mod-host] Add midi (plugins connections) support

[SrMouraSilva]

Mod-host contains some commands for audio plugins. Mod-ui enables connect midi to pedal:

How connect a midi in effect?

• Install https://github.com/x42/midifilter.lv2#install
• execute

./mod-host -i
mod-host> add http://gareus.org/oss/lv2/midifilter#cctonote 1 
mod-host> add http://guitarix.sourceforge.net/plugins/gx_redeye#chump 2 
mod-host> add http://gareus.org/oss/lv2/midifilter#cctonote 3
mod-host> connect effect_1:midiout effect_3:midiin
mod-host> connect effect_1:midiout effect_2:in

Mod-host uses the same command for connect audio in/out ports and connect midi in/out ports.

Implementation

Example midi effect: uri: http://gareus.org/oss/lv2/midifilter#cctonote (contains midiin and midiout)

• Create MidiPort
• Create MidiInput
• Update MidiInput docs
• Create MidiOutput
• Update MidiOutput docs

---

#67

• [ ] Create ConnectableMixing
• [ ] Update MidiOutput to use ConnectableMixing
• [ ] Update Output to use ConnectableMixing

---

• Create effect.midi_inputs list
• Create effect.midi_outputs list
• Create Lv2MidiInput
• Create Lv2MidiOutput
• [ ] Create MidiConnection?
• [ ] Doesn't enable connection between (audio) input and midi_output or (audio) output and midi_input ConnectableMixing
• Adapt PersistenceDecoder to make midi connection
• Add mod-host support

---

• Create SystemMidiInput
• Create SystemMidiOutput
• Adapt SystemEffect for receive midi ports in constructor
  

  PluginsManager/pluginsmanager/model/system/system_effect.py

  Lines 65 to 66 in e008fd3

  	def __init__(self, representation, outputs, inputs):
  	super(SystemEffect, self).__init__()

• Change JackClient for obtains audio inputs, audio outputs, midi inputs and mid outputs.
  

  PluginsManager/pluginsmanager/jack/jack_client.py

  Lines 63 to 65 in e008fd3

  	self.client.activate()
  	def close(self):

• Adapt SystemEffectBuilder for create SystemEffect with midi ports

  PluginsManager/pluginsmanager/model/system/system_effect_builder.py

  Lines 18 to 38 in e008fd3

  	class SystemEffectBuilder(object):
  	"""
  	Automatic system physical ports detection
  	:param JackClient jack_client: :class:`.JackClient` instance that will get the information to
  	generate :class:`.SystemEffect`
  	"""
  	def __init__(self, jack_client):
  	self.client = jack_client
  	def build(self):
  	inputs = []
  	outputs = []
  	for port in self.client.client.get_ports(is_audio=True, is_physical=True):
  	if port.is_input:
  	inputs.append(port.shortname)
  	else:
  	outputs.append(port.shortname)
  	return SystemEffect('system', tuple(outputs), tuple(inputs))

How to test

• Not mock - https://github.com/PedalController/MidiPedalController/issues/1#issuecomment-284382499
• Mock

How will works

pedalboard.connect(effect2.midi_outputs[0], effect.midi_inputs[0])
or 
pedalboard.connections.append(MidiConnection(effect2.midi_outputs[0], effect.midi_inputs[0]))