FIX Broken test cases

[caseyfleeter]

There are 4 broken test cases which need to be repaired:

• Case 06: The has a segmentation fault, potentially because the IMPEDANCE boundary conditions aren't properly implemented? (see issue Boundary Conditions (outlets) to Reimplement and Test #22 )
• Case 07: Invalid datable type "WAVE". This is currently working with type "LIST" for the WAVETABLE, but we should check the WAVE boundary condition as well. (see issue Boundary Conditions (outlets) to Reimplement and Test #22 )
• Case 08: Area goes negative (check_pos() fails). This means the area of a segmentation is negative. The amount of pressure in the model may not be high enough, so the R BC should be changed.
• Case 15: Area goes negative (check_pos() fails). This means the area of a segmentation is negative. Number of finite elements/segment may need adjustments.