Minimizing headers complexity

[dimitre]

Some measures were made in previous PRs trying to reduce .h includes in .h files And there is room for more optimization.

PRs

• https://github.com/openframeworks/openFrameworks/pull/7779
• https://github.com/openframeworks/openFrameworks/pull/7784
• https://github.com/openframeworks/openFrameworks/pull/7792
• https://github.com/openframeworks/openFrameworks/pull/7815

Other related

• https://github.com/openframeworks/openFrameworks/pull/7918
• https://github.com/openframeworks/openFrameworks/pull/7908

Done in previous PRs

• [x] changing #include to forward declarators when possible;
• [x] changing #include to template forward declarations when possible;

Done, but can be improved

• [ ] Reducing utilizing headers include inside other headers, try to explicitely declare needed headers. example of something that can be improved: ofParameter.h includes ofPoint which includes ofVec3f (inline only) which adds ofVec2f and ofVec4f one useful tool is the compiler (clang fork) include-what-you-need easily installed via brew in macos.

Next Ideas (we can discuss each one)

• [ ] https://github.com/openframeworks/openFrameworks/issues/7814
• [x] Substitute including ofConstants.h in headers that use only for deprecation and favor c++14 [[deprecate]]
• [ ] move ofVec3f inline functionality for a cpp file
• [ ] converting some regular objects used only once in header files to pointers (unique_ptr) so their includes can be replaced by forward declarators