ETV: use enum and command line options for the test cases

ETV: added more specific conditional statements for the in/outflow formulations

Default P_inlet 1. -> 1.e3 so that it becomes 1 after the unit conversion

fixed the bug in Euler context (Setup and surface contexts still don't work for advection(2d))

style

WIP: (BUG) fixed in/outflow formulations but there is a bug in the context and also advection(2d) breaks

mms BCs -> wall BCs

added Euler_Sur

Added required variables to surface context

removed some todo comments

removed periodicity

Initial commit for replacing periodic BCs with in/outflow BCs => added support for in/outflow in navierstokes.c

some clean-up

removed the forcing term of case 4

style

Added the forcing terms for case 4 though it is disabled...still seeing large error

Made some changes to the tests

style

WIP: Debugging: added 4 tests for debugging but there is still a problem in the last one

convergence_plot.py: changed the first color to stand out

convergence_plot.py: modified to plot loglog

gitignore: adding *.png for ignoring convergence plots

Debugging: q[3]=0 since we have slip bc in the z direction

verification-test.sh: specify number of faces in the z direction = 1

Debugging: perform the tests in one ts to investigate the bugs in the spatial discretization