#2309: have simfactory's "run" user command log output to files as well as screen

Comment (by Roland Haas):

This pull request: https://bitbucket.org/simfactory/simfactory2/pull-requests/36/simrestart-duplicate-log-data-to-file-in/diff is a pure python solution making use of simfactory’s existing assumption on the name of the log file. It requires some low level POSIX calls.

Please review.