This patch contains two additions to simplenode.runner:
1. Check if vm.args exists in CWD; if so, use it. This makes it
easier to start multiple concurrent nodes on a single machine
from one rebar-created release (starting each node from its
own directory, with its own copy of vm.args and e.g.
sys.config, log directory, database directory, etc.)
2. Add the targets start_boot <file> and console_boot <file>.
This is used to select a different boot script. The 'setup'
application (http://github.com/esl/setup) builds a special boot
script for installation (all apps loaded but not started,
making it possible to run install hooks with the full code path