Update changelog

Update changelog
robustify test_block_master_ports
optimize test_catchup_exercises
optimize torture tests
optimize test_concurrent_collapse_fails
fix calculation of lease expiration for small numbers (should start from a float)
Merge pull request #320 from Incubaid/half-lease-calculation

fix calculation of lease expiration for small numbers (should start from...
fixes build of debian packages
optimize test_sabotage
Merge pull request #319 from Incubaid/robustify-test-block-master-ports

robustify test_block_master_ports
Merge pull request #321 from Incubaid/debian_fix

fixes build of debian packages
Merge pull request #322 from Incubaid/optimize-tests

Optimize tests
Merge branch '1.7' into qshell_cherry

Conflicts:
	pylabs/test/server/right/system_tests_long_right.py