Merge branch 'feature/mc-linearise' into 'master'

feature/mc-linearise

I got a little fed-up with having to open the xml and remove the <Curved> tag section to linearise the mesh (a step needed for the linear elastic solver). Doing this manually was a nightmare with large meshes.

This module for meshconvert simply goes through all the edges and faces and removes the high-order nodes.

See merge request !509