Allow setting units of the z dimension in IceModelVec3Custom.

This should be ported to 0.6.
a ref.
more ref work
yet more ref fiddles (YMRF)
Save CTS when -o_size big is set. See #262. Port to 0.6.
Remove undocumented storglaciaren example from users manual.  Port to 0.6.
The "init. step" of couplers is a method now. Port to 0.6.

Also: re-initialize surface and ocean models at the very end of the
model setup to get rid of side-effects of this step.
Very minor cleanup. Port to 0.6.
Fix snow depth reset code. Port to 0.6.
PDD sub-intervals consistent with interpolation scheme. Port to 0.6.
Initialize variables in PDDMassBalance::step(). Port to 0.6.
-surface_given_period X should take an integer X. Port to 0.6.
Add -timestep_hit_multiples. Port to 0.6.

Also: refactor adaptive time-stepping code and document new adaptive time-stepping decision output. See #259.
IceModel::skip_counter() *returns* result.
Remove the "preliminary time-step duration" parameter.

The preliminary time-step itself was removed by 03c8571.
Update the Ross run scripts.

(There is no "preliminary" step now.)
Correct some doxygen comments.
Update the gradient method test case.
Fix discharge reporting. Port to 0.6.
Fix a typo in IceModel::step() (in dev).