Set CYLC_VERSION then source .profile, for cylc access.

Used at the top of job scripts to give tasks access to cylc, and as the
first part of event handler and job poll and kill command strings so
that they also run under the same version of cylc as the calling suite
(event handlers may call cylc commands). This allows users to run suites
under multiple cylc versions at once by setting PATH according to the
cylc version.
Remove unnecessary space after newline character.
Added CYLC_VERSION to the transplantable environment for detaching tasks.

This commit also tidies some comments in the job script.
Updated the examples/detaching suite a bit.
Merge pull request #507 from hjoliver/471.find-cylc-on-task-hosts

Set CYLC_VERSION then source .profile, for cylc access.