- for Qt 5.15: added missing #include statements that became necessary since Qt 5.15
- for Qt 5.15: fixed use of several deprecated functions
- for Qt 5.15/6: removed usage of QMatrix
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
new: iterator interface and improved documentation for JKQTPDatastore
reorganization of library (better separation of common code in jkqtpcommon and other code e.g. in jkqtplotter or jkqtmathtext)
