implemented functionality to delete a certain kind of element from the mesh (this might be used to remove line-elements from 2d/3d meshes). the method is currently not called because the conditions under which it should be used are not quite clear.

added open/save/remove buttons in tab-widgets; added reload button for recalculating colorlookup-table for active scalar; fixed issue with incorrect display of active scalar array name; fixed issue with mesh quality not being scaled correctly; added scheme for enabling access buttons only when needed

finally renamed dataview appropriately;  restructured load/save/remove structure for meshes as a prototype for the other widgets

Set c++11 std for gnu and intel compilers.

Vislab export functionality

OGS_DONT_USE_OPTIONAL_SUBMODULES should be set to ON on Travis builds.

Use stl in base lib

This also removes uniqueVectorInsert(). The new function is working for all containers, which provide begin() and end() and typedef value_type.

Equivalent STL call is std::binary_search(array.begin(), array.end());

Moved third-party libraries and submodules to ThirdParty/