!!Running SimTree

SimTree always requires a valid StudyRoot to work. This is a directory in the
filesystem where all data related to a simulation study is located.
SimTree selects the StudyRoot in the following sequence:

When the [@o]--study-root option with a directory name as argument is given, this
directory is selected. When the environment variable SIMTREE_STUDYROOT is
defined, the value of this variable is taken as the StudyRoot. If neither [@o]--study-root
is given nor SIMTREE_STUDYROOT is defined, the current directory is selected. In
any case, the StudyRoot must exist.
