Different options are set as `feature`, also every possible plugin,
but this may cause confusion.
All options set as `feature` but plugins have been made `boolean` to
avoid further confusions.
`help2man` is also installed in the CI image because is required to
build different libraries.
meson is a build system focused on speed an ease of use, which
helps speeding up the software development. This patch adds meson
support along autotools.