setup of basic structure
setting element status and getting total numbers of nodes and elems
returning active nodes and elements vector
setting status based on mat id and returning active elements for a node
added comments
changed return type for connected active elements of a node to unsigned int
introduced element IDs
added algorithm-include to FixedTimeStepping to avoid compile error
added method for setting status to all elements, added tests
changes based on PR comments
changed iterators to constant functions where possible
adapted id parameter type for element classes
changed argument order for tests
Merge pull request #362 from rinkk/ActiveElementExtension

Managing active/inactive elements and nodes