Minor change of the configure.bat file.
Code cleanup in wrappers of GL objects

- Removed the noexcept initialization functions that
  were superseded by the Optional<Object> modifier template.
Minor change in the implementation of Array
Reorganization of the test directory

- Moved the contents of the test/ directory to test/oglplus/.
Minor change in the build system.

- Moved the oglplus-advanced-examples target to parent CMakeLists file.
Minor changes in ops/application

- Removed dependencies on String and config.hpp
Multiple changes

- Added #undef MemoryBarrier to context/synchronization.
- Added explanatory notes, why it is necessary.
Minor updates in the Spectra advanced example
Update of the build system and tools

- Reimplemented the logic for indicating the requirements and dependencies of examples.
- Updated the examples to indicate which texture or other resources they are using.
- Updated the build system to make examples dependent on textures which they use.
- Updated gl.hpp, added #ifndef OGLPLUS_NO_SITE_CONFIG around the include
  of the generated site_config.hpp header.
Update of the build system

- Added a check if threads are working.
- Updated requirements for examples requiring threads.
Removed the devel directory

- Also updated the _git/info/exclude file.
Update of the build system

- Added correct handling of return codes from cmake
  in the configure.py script.
- Added dependencies and requirements for example harnesses.
- Reimplemented the code checking for harness requirements
  and adding harness dependencies to be more scalable.
- Updated the requirements of some of the examples.
Multiple changes

- Backporting and minor fixups in the Spectra advanced example.
- Fixed build problems with the Spectra example on Windows.
- Updated the multithreading-related classes used in the examples.