<timeout> configuration parameter

[mkarg]

Sometimes it happens that the execution of an external task is stuck infinitely, e. g. when a platform specific executable runs into an unforeseen condition where it asks for user input, but the user of the maven exec plugin thought it won't ask anything at any time.

To prevent this, it would be good it a <timeout> parameter (default: inifinite) could be given which will fail the build once the executable needs longer than the given timeout.

[mkarg]

@rfscholte If you think this is a good idea, I would be happy to provide a PR. :-)

[mkarg]

🎉