MAJOR: mworker: remove program section support

MAJOR: mworker: remove program section support

This patch removes completely the support for the program section, the
parsing of the section as well as the internals in the mworker does not
support it anymore.

The program section was considered dysfonctional and not fully
compatible with the "mworker V3" model. Users that want to run an
external program must use their init system.

The documentation is cleaned up in another patch.