Merge pull request #18 from Tomokayama/thomas_working

Taking in TK's progress.
Merge pull request #19 from Tomokayama/thomas_working

First Implementation of Richards Flow (results not 100% correct yet)
Change the PCS_TYPE to RICHARDS_FLOW, so that the numerical settings will be recognized and converted into OGS6 data structure respectively. After this change, the PICARD iterations will be executed.
Change the order to supporting points in the input files.
This is due to a potential error in the file
\ogsCore\MathLib\Interpolation\LinearInterpolation.cpp
Tom Fischer has been notified regarding this bug.
u_k0 should be supplied here instead of u_k1.
The original code will prevent the current value vector from getting initial values specified by the user.
Nori has confirmed that it was an error in the previous code.
This is my fault.
After comparing with the code in OGS5, it is clear that the term added to the right-hand-side does not contain water density term. Now the simulated value should be correct.
Merge pull request #3 from HaibingShao/AddRichards

Add richards