Add executable summarizing time stepper properties

[wthrowe]

$ bin/TimeStepperSummary --sort 'stab/esubs'
name                 order subs esubs stab   stab/subs stab/esubs IMEX LTS 
---------------------------------------------------------------------------
AdamsBashforth[8]    8     1    1     0.0122 0.0122    0.0122     N    Y   
AdamsBashforth[7]    7     1    1     0.0233 0.0233    0.0233     N    Y   
AdamsBashforth[6]    6     1    1     0.0439 0.0439    0.0439     N    Y   
AdamsBashforth[5]    5     1    1     0.0817 0.0817    0.0817     N    Y   
AdamsMoultonPc[8]    8     2    2     0.264  0.132     0.132      N    N   
...

Proposed changes

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[nilsdeppe]

LGTM! Clang-tidy wants some gsl::ats. I think this will be really useful. Something I've definitely wanted :D

[wthrowe]

Fixed ats. Also moved <boost/program_options.hpp> from the top into the main include list because I have no idea why I put it separately.