Tried to improve the wording a bit.

See merge request Obarun/66!32

# Conflicts:
#   doc/html/66-update.html

adds field @extdepends. Services declared with @optsdepends are not mandatory. Services declared with @extdepends must have the frontend file installed at least

make a distinction between system error and unable to find the service, return -1 on system error, 0 for service error

Bugs fix: set uid array to zero, retrieve the old behavior at unsupervise proccess and do not die if we can't stop services properly