Cmake cleanup

[meshula]

This commit allows a full cmake build.

• consolidate options at the top level
• detect a "reasonable" place to install the python components
• restrict gcov coverage to platforms that support it (those built with gcc)
• use cmake build from setup,py on all platforms (cmake will call make appropriately, so the outcome is identical to how it was)
• update submodules (any/optional/etc) BEFORE installing them
• add ability to build OTIO libraries as static
• add optional debug postfix because windows release/debug builds are not compatible
• add platform appropriate rpaths (@loader_path on Mac, $ORIGIN on Linux)
• add ability for cmake to do an install into the python environment so that a cmake build automatically results in a functional python build
• more granular build control (turn python builds or c++ builds on or off independently)
• For IDEs, rename the .sln or .xcode file to OpenTimelineIO (was OPENTIMELINEIO_ROOT)

[codecov-io]

Codecov Report

Merging #837 (55489b9) into master (5aa24fb) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #837   +/-   ##
=======================================
  Coverage   84.18%   84.18%           
=======================================
  Files          74       74           
  Lines        3061     3061           
=======================================
  Hits         2577     2577           
  Misses        484      484           

Flag	Coverage Δ
unittests	84.18% <ø> (ø)

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[meshula]

Related: #813

Before merging, I need to test pip's --target directive to make sure the target is properly transmitted to the cmake script.

[meshula]

Maybe related: #838 ~ If there is a more general PyInstaller issue, we could reopen 838 after this PR is merged.

[Tilix4]

Thanks! I confirm this will solve #813. I've tested the --target option and it works well on my windows.

Thanks, hope this will land soon :)

[ssteinbach]

couple of really small questions around commenting and removing some debug statements