Updated default DOCKER_PORT in nat rule

the `DOCKER_PORT` can be changed for the `host` but have to be `4243` in the guest
add Option to get settings from external config file
if you kill the VBoxHeadless process, the state is set to aborted (happend to me when I ran out of memory) - with this PR you can delete it as though it were stopped on purpose
Merge pull request #98 from SvenDowideit/allow-delete-of-abort-status-vm

if you kill the VBoxHeadless process, the state is set to aborted (happe...
Merge pull request #97 from aheissenberger/feature/pull/optional-config-files

get settings from external config file if exists
Merge pull request #94 from moul/patch-4

Updated default DOCKER_PORT in nat rule
Merge remote-tracking branch 'upstream/master'