Replace deprecated numpy types

[guyer]

Recent NumPy versions (~1.20) raise a number of deprecation warnings:

• "np.bool is a deprecated alias for the builtin bool" in fipy.variables.variable
• "np.int is a deprecated alias for the builtin int" in skfmm
• "Converting np.character to a dtype is deprecated" in tvtk
• "'TraitPrefixMap' trait handler has been deprecated" in tvtk

[guyer]

Remaining failures are unrelated to this PR:

• TravisCI
  • circleQuad example fails with Gmsh > 4.4
  • PyTrilinos is not installing correctly
• CircleCI
  • conda2_env has problems
  • polyxtal freezes with Py3k and scipy solvers
  • circleQuad example fails with Gmsh > 4.4
• AppVeyor
  • Vtk is not installing correctly on Py3k
  • circleQuad example fails with Gmsh > 4.4

[tkphd]

Seems reasonable. I have not tested locally, but confirmed that the CI errors are unrelated. LGTM.

[guyer]

I've added more changes of the same character, although in these cases, the deprecations are not in our code, so I've silenced the errors in the tests, rather than doing anything useful to make the deprecation go away.

• skfmm has already been fixed and just needs to percolate to pip.
• tvtk has been fixed, but we're getting mayavi 4.7.1 instead of 4.7.2 for some reason. Regardless, my hope is to excise it completely in the rather short term.

[guyer]

A better picture of the test status can be seen in the integration tests at #799

[tkphd]

All checks pass in #799. Yeet those types.