Library Header Changes

* Set some good defaults for header order, widths, and show/hide values with
an eye on a really good first-run experience.
* Delete header_state values on upgrade, since we can't use them
across db versions.
Merge branch 'master' into columns-reset-to-default
Make sure to clear out all header states
Make most models inherit the default hidden-column settings.
Make column name / widths easy to set up.
better comment
no need to change old schema update processes
Do the header_state reset in schemamanager.cpp
Fix math error in source rectangle for horizontal VU meter peaks.
Deere fixes.

* make knob line ends round
* SVG "rgba" is not supported by Qt. Use stroke-opacity and fill-opacity instead.
Rename EffectChain parameter to super.

Named the EffectChain control 'super1' for expansion. Updated Shade,
Deere, and LateNight. Fixes Bug #1378211.
Remove DOS line endings.
Update ControlPickerMenu for superknob CO change.
Merge branch 'columns-reset-to-default' into headerstate
Add custom library header save/restore code.

Should migrate current 1.12 installations from the old QT binary blog
to the new protobuf format.  This won't help us for users upgrading
from 1.11, but all future upgrades should be much smoother.
Includes a small roundtrip test.
nicer debug log
Merge branch 'columns-reset-to-default' into headerstate
need the proto file
Fix migrating from the old blob
Remove loading of resource path from mixxx.cfg.

Fixes issues with using multiple versions of Mixxx on the same
machine. Bug #1392854.
Process cover art when loading tracks from browse mode or external libraries.

Partial fix for Bug #1393749.
Make the internal representation of the header state the proto itself