Quadratic interpolation for direct forcing.

* Allow QUADRATIC as a command line or input file option.
* Add new vectors to hold extra cell indices and coefficients.
* Calculate the correct coefficients in tagPoints.
* Modify generateL and updateRHS1 appropriately.
Add convergence cases for quadratic interpolation.
Merge branch 'master' into quadratic-interpolation

* Resolved a conflict with tagPoints.inl.
Print eta values for direct forcing method.

* Analyze eta values in analyzeTags.py.
* Edit related files.
* Change output file type in cavityRe100.py to pdf.
Add convergence cases for 25x25 and 30x30 grids.
Write solver for Diffusion with immersed boundary.

* cavityRe100.py: Print convergence rates for a general number of grids.
* Calculate the average eta for 2-D direct forcing.
* Fix direct forcing case for cylinder with linear interpolation.
* Add cases for DiffusionSolver convergence test.
Merge branch 'quadratic-interpolation'
Add explicit pressure term to FadlunEtAlSolver.

* Add 25x25 and 30x30 convergence tests for FadlunEtAlSolver.
Include explicit pressure term in FadlunEtAl.

* No explicit pressure term in DirectForcing.
* Changes to cavityRe100.py.
  * Ignore FutureWarnings.
  * Calculate order of convergence for all velocities taken together.
  * Cleaner output.
* Run diffusion test cases for 4000 time steps.
* Delete all quad test cases.
Add test cases uquad and vquad.

* For both DirectForcing and FadlunEtAl.
* Add constant interpolation cases for Diffusion.
* circ_30 linear case.
* Place font selection action inside try block in python scripts.