Improve port and process management

Add isBindableByProc which uses /proc/net to search available port.
Change userPorts-range from [49152..65535] to [5001..32767].
 ([49152..65535] is os-port-searching area.)
Add cleanUpProcesses which stops process-groups when test is finished.
Add runSB and withSandbox funtions for unit-test
I think this is linux-specific code. Please consider using a compile switch here.
http://blogs.operationaldynamics.com/andrew/software/haskell/config-dot-h-and-ifdef