Better examples in documentation

[mrp089]

Change the examples in the documentation. Use current test cases and only mention currently tested functionality (#53).

[mrp089]

I changed the documentation:

• removed old examples
• add example for simple tube with resistance boundary condition (test case, analytical results, simulation results)
• add example for bifurcation with RCR boundary conditions (test case, literature reference, simulation results)

@melodydong I had to change the test case bifurcation_RCR.in to match the results in [xiao13] (elastic wall, distal resistance in RCR, number of cycles, smoothness of inflow profile, test values). The results seem to match with the ones in Figure 11.

[mrp089]

Update documentation of supported boundary conditions (BCs):

• delete BCs that are no longer supported
• distinguish between inlet and outlet BCs