Meter-adapted duration subdivision

First, duration subdivision: notes, rests, dots and ties.

Subdivision of notes and rests is now based on metric analysis. 
Here are some examples:

- long note in center of bar: 
https://docs.google.com/file/d/0B5alKuFoSol2MjQ0d0JNRVNwZms/edit?usp=sharing

- long pause in center of bar:
https://docs.google.com/file/d/0B5alKuFoSol2U3pkU1UwQUF2cEE/edit?usp=sharing

- pauses and chords near beats:
https://docs.google.com/file/d/0B5alKuFoSol2bWtZRGlYeXUycEE/edit?usp=sharing

- half rest at the start or at the end of 3/4 bar:
https://docs.google.com/file/d/0B5alKuFoSol2OTFTSWpTUTdpTlU/edit?usp=sharing

- larger piece of music:
https://docs.google.com/file/d/0B5alKuFoSol2d3Yxbm5jTEYtM00/edit?usp=sharing

- last quarter rest in compound meters like 6/8:
https://docs.google.com/file/d/0B5alKuFoSol2eHM5emtXTnR6cGc/edit?usp=sharing

- different pauses:
https://docs.google.com/file/d/0B5alKuFoSol2U0ZtM25YaVY1dlk/edit?usp=sharing


Another new feature is a tree-view based frame for selection of MIDI import operations. Now for multiple tracks, if the first row is selected then operations are applied for all tracks simultaneously.

Also there are some changes in MIDI quantization.

MIDI import tests were slightly adapted to new settings. Quantization value is set from program preferences. Test scores were modified in a similar manner: a pair of half and quarter rests were exchanged in each score. No more changes in tests.

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trig-ger