cmake: Sample/Examples/Tests Layout Rework

[Mizux]

Currently we only have SAMPLES (or-tools/<component>/samples) and EXAMPLES (examples/*).

I propose to:

• Move lang test to ortools/<component>/<lang>
  e.g. ortools/sat/java/CpModelTest.java
• Add a BUILD_TEST option to only build what is currently located in examples/tests
• Move tests to or-tools/<component>/tests
• Add option to control if binaries or source are installed e.g.
  • INSTALL_SAMPLES_BINARIES to install samples binaries (to CMAKE_INSTALL_BINDIR)
  • INSTALL_SAMPLES_SOURCES to install samples source code (to CMAKE_INSTALL_DATADIR)
• Add a General and <LANG> options e.g. INSTALL_SAMPLES_BINARIES, and INSTALL_CXX_SAMPLES_BINARIES

note: For python while binary and sources file is identical (i.e. the .py file) it will be installed in BINDIR and/or DATADIR according to the option enabled.

Any feedback welcome !

[Mizux]

After reflexion examples/tests should be empty since these tests/issues should be in the test files of the itself.
So the priority is to export all C++ unit tests to github, got coverage report and remove examples/tests/ on the long run...