Removed suite block/unblock commands and functionality.

This ancient feature was really not very useful. Telling a suite to
refuse to comply with your own commands is a bit like telling the unix
'rm' command not to delete anything until further notice.
Request handling in a background thread.
Turned on multi-threading in the Pyro daemon.
Wider tolerances (timing) on some reference tests.
Make suite state summary update atomic.

The fact that it wasn't matters for continuous requeset handling.
Connect just the new task message receiver to the network.

Previously the task proxy object itself was connected, but we should not
allow clients to make direct calls to other task proxy methods anymore.
Command request queue.
Do task job submissions a worker thread.

Also took some helper classes out of scheduler.py.
Added Dave's Evil Load Test.
Fixed typo in dev test suite.
Exception handling for gcylc reconnection.

gcylc was dropping a traceback on suite exit.
Relaxed ref test timouts
Restored broadcast functionality.
Cleaner use of flags to trigger processing.

And always print task process loop timing in debug mode.
Merge pull request #205 from hjoliver/remove-block-and-unblock

Remove block and unblock
Merge branch 'master' into 194-multi-threading

Conflicts:
	bin/cylc-block
	bin/cylc-unblock
	lib/cylc/gui/SuiteControl.py
	lib/cylc/remote_switch.py
	lib/cylc/scheduler.py
	lib/cylc/state_summary.py
Minor change to a Jinja2 example suite.

The examples/jinja2/defaults suite had (deliberately) a template
variable with no default set, requiring use of the new --set command
line options. However, this broke automated validation of all example
suites.
Repeating asynchronous tasks need instance-specific environment vars.

Recent changes moved [runtime] environment to a class variable, updated
by broadcast (if necessary) at the last minute. So, now also update the
enviroment dict with instance-specific environment variables, if any, at
the last minute. To test run the examples/satellite/ suite.
Trivial documentation update.
Improved release tarball script, via the main CLI.

Uses 'git describe' to generate the release version string.