adding the set function to update boundary node concentration values.
set concentrations
clean mat_vprime after usage.
store given known x and apply them when solve() is called
apply Knwon solution in solve
move apply bc from construct() to solve()
Merge pull request #45 from norihiro-w/react_trans_GIA

fix imposing BCs to dense equations
Merge branch 'react_trans_GIA' of github.com:HaibingShao/ogs into react_trans_GIA
Merge pull request #44 from zolfagha/react_trans_GIA

restting vprime matrix. fixing BC for concentrations
a second choice of using LIS solver.
move the minimization solver to the destructor.
Merge branch 'react_trans_GIA' of github.com:HaibingShao/ogs into react_trans_GIA
Merge pull request #13 from HaibingShao/react_trans_GIA

React trans gia