[wt4] fix index issues in initproblem
Merge pull request #36 from Xarthisius/wt4_fix

[wt4] fix index issues in initproblem
[wt4] updates to problem.par
[wt4] ensure that registering initial variables occurs only once
[wt4] IC file should be read only once
[wt4] replaced some magic numbers with named constants
[wt4] deallocate working array
Merge pull request #37 from gawrysz/wt4_update

Wt4 update
[multigrid_gravity] allow residuals to be computed on a selected level
Merge pull request #38 from gawrysz/mg_residual_on_level

[multigrid_gravity] allow residuals to be computed on a selected level
adjusted whitespaces
added some warnings and checks
spelling
Merge pull request #39 from gawrysz/cosmetics

Cosmetics