reduce description noise - provide default specs for midiMsgType / type

[adcxyz]

// current verbose notation:
('midiMsgType': 'cc', 'type': 'slider', 'midiChan': 0, 'midiNum':  ccnum, 'spec': 'midiCC')
// slider could be shortened to :
('midiMsgType': 'cc', 'type': 'slider', 'midiNum':  ccnum)
// because midiChan is 0 by default unless overwritten.
// and spec midiCC can be inferred from midiMsgType unless overwritten.

[sensestage]

I would prefer to have an explicit definition of midiChan

[sensestage]

automated spec is ok for me

[LFSaw]

+1 for explicit definition...
automated spec ok but should be visibly documented in the helpfile.

[adcxyz]

actually not necessary. currently \spec is a required key to distinguish dicts which describe elements from dicts which are groups of elements.