Adding an option to adapt the linear system convergence tolerance adaptively (in combination with Nonlinear System Convergence Measure = residual)

git-svn-id: svn://svn.code.sf.net/p/elmerfem/code/trunk@6721 04224531-1f84-46d8-96ce-875b9e37dce3
WhitneyAVHarmonicSolver: The use of new edge basis functions based on the Piola transform enabled

git-svn-id: svn://svn.code.sf.net/p/elmerfem/code/trunk@6722 04224531-1f84-46d8-96ce-875b9e37dce3
Fixed some collaboration difficulties between ShellSolver and HelmholzSolver in order to be able to compute acoustic fields caused by vibrating shells. 


git-svn-id: svn://svn.code.sf.net/p/elmerfem/code/trunk@6723 04224531-1f84-46d8-96ce-875b9e37dce3