NEW/BREAKING: refactor CMake-Code, so static/dynamic switch is done via <code>BUILD_SHARED_LIBS</code>, which retires <code>JKQtPlotter_BUILD_STATIC_LIBS</code>, <code>JKQtPlotter_BUILD_SHARED_LIBS</code> and removes the capability to build static and shared libraries in one location (fixes issue #104)
NEW: prepareed library for CMake's <a href="https://cmake.org/cmake/help/latest/module/FetchContent.html">FetchContent</a>-API
NEW: the different sub-libraries JKQTPlotter, JKQTFastPlotter (DEPRECATED), JKQTMath, JKQTMathText can be activated/deactivated with CMake options JKQtPlotter_BUILD_LIB_JKQTPLOTTER, JKQtPlotter_BUILD_LIB_JKQTFASTPLOTTER, JKQtPlotter_BUILD_LIB_JKQTMATHTEXT, JKQtPlotter_BUILD_LIB_JKQTMATH
1. added several new (JKQTPMathImageBone, JKQTPMathImageCool, JKQTPMathImageCopper, JKQTPMathImageAutumn, JKQTPMathImageSeismic, JKQTPMathImageTerrain, JKQTPMathImageViridis, JKQTPMathImageMagma, JKQTPMathImageInferno, JKQTPMathImagePlasma)
2. reworked LUT-types (now a QVector, instead of a C-array, suing malloc)
3. reworked available functions to build LUTs (cleanup, more options, clearer names)
4. added functions to load palettes from files
5. Improved documentation
* added example for user-controlled color palettes
