Doxygen: Fixed broken link from general revision history to Core(A) h…

…istory.

Added current date for development release 5.2.1-dev3.

Pack: Added release date for 5.2.0

Updated generated documentation for release 5.1.1

CMSIS 5.1.0 online documentation

updating prebuild documentation for 5.0.1

setting pack release version for public 5.0.0

Interim version for seeking feedback from a wider audience.