merge meep::quiet and fields::verbose into a single meep::verbosity

[stevengj]

The problem with fields::verbosity was that it was not available in structure etcetera, and meep::quiet is not fine-grained enough to specify ordinary output vs. extra debugging output. This PR merges both into a single meep::verbosity global integer: 0 is quiet mode, 1 (the default) is ordinary output, and 2 is extra debugging output.

The Python meep.quiet() function still works and sets verbosity to 0, and now there is a lower-level meep.verbosity(value) routine that you can use to set the verbosity level explicitly.

[oskooi]

The following error appears when I use mp.verbose(2) before sim.init_sim():

raceback (most recent call last):
  File "grating.py", line 159, in <module>
    main(args)
  File "grating.py", line 116, in main
    mp.verbose(2)
AttributeError: module 'meep' has no attribute 'verbose'
Traceback (most recent call last):
  File "grating.py", line 159, in <module>
    main(args)
  File "grating.py", line 116, in main
    mp.verbose(2)
AttributeError: module 'meep' has no attribute 'verbose'

Also, the following error appears whenever I use mp.quiet(True):

Traceback (most recent call last):
  File "grating.py", line 158, in <module>
    main(args)
  File "grating.py", line 116, in main
    mp.quiet(True)
  File "/usr/local/lib/python3.5/site-packages/meep/simulation.py", line 2927, in quiet
    mp.cvar.verbose = int(not quietval)
AttributeError: Unknown C global variable 'verbose'
Traceback (most recent call last):
  File "grating.py", line 158, in <module>
    main(args)
  File "grating.py", line 116, in main
    mp.quiet(True)
  File "/usr/local/lib/python3.5/site-packages/meep/simulation.py", line 2927, in quiet
    mp.cvar.verbose = int(not quietval)
AttributeError: Unknown C global variable 'verbose'

[stevengj]

The function is mp.verbosity(2), not mp.verbose(2).

quiet is fixed in 55a67ae, sorry.

[oskooi]

The same error occurs with mp.verbosity(2).

Using MPI version 3.0, 5 processes
Traceback (most recent call last):
  File "oled.py", line 99, in <module>
    mp.verbosity(2)
AttributeError: module 'meep' has no attribute 'verbosity'
Traceback (most recent call last):
  File "oled.py", line 99, in <module>
    mp.verbosity(2)
AttributeError: module 'meep' has no attribute 'verbosity'
Traceback (most recent call last):
  File "oled.py", line 99, in <module>
    mp.verbosity(2)
AttributeError: module 'meep' has no attribute 'verbosity'
```

[oskooi]

This should be mp.cvar.verbosity = verbose_val. Nevermind, this was also fixed by 55a67ae. However, the error persists even with this commit.

[stevengj]

@oskooi, the error about meep.verbosity should be fixed by 268183a