bump versions and release 1.6.0

update build with maven dependencies, flexmark 0.64.4

update docs

bump version

update readme

change code to use command argument class

remove code tag in label

add plugin-util module to project, revert expansion of _SRCS/_HDRS name

resolve white space preservation when generating CMakeLists.txt

fix a few deprecation warnings, Add toolchain option - not bundled