Adapt YamlImpoter to new constructor of Task and Testcase
Bump psutil version in REQUIREMENTS.txt
Adapt task type Communication to new sandbox

Fixes #126
Communication: Use a better hard-coded indexes to avoid future breakage.
cmstestsuite: Add basic tests for communication tasks.
Communication: Eliminate unnecessary open/close noise.
cmstestsuite: Preserve log files from clean-checkout tests.