Added possibility to remove zeros from the linear system upon solution. This should be used with care since it may result to failure of assembly process next time. Mainly a feature to detect bloated memory usage due to unnecessary zeros and study their effect. 


git-svn-id: svn://svn.code.sf.net/p/elmerfem/code/trunk@6715 04224531-1f84-46d8-96ce-875b9e37dce3
Added the possibility to have a diagonal weighted projector in the case there is a on-the-fly created discontinuity in the mesh. This makes the projector smaller and seems to have a favourable effect on the iteration count without much effect on the results.


git-svn-id: svn://svn.code.sf.net/p/elmerfem/code/trunk@6716 04224531-1f84-46d8-96ce-875b9e37dce3