#119: rename cycle time to cycle point

This renames usage of `cycle time` and `CYCLE_TIME` to
`cycle point` and `CYCLE_POINT`. All cycle time input names
(e.g. `[scheduling]initial cycle time`) are deprecated.

The environment variables `*_CYCLE_TIME` are kept for
backwards compatibility with third-party scripts.

This should not be merged until it has been updated with
the result of #997, so that the test-battery passes.

@hjoliver, please review.
I need to revisit some of these ancient bits of the user guide, some of which came from what was originally intended to be a paper (a user guide shouldn't really have an abstract, for instance).