#2260 delete migrated cells using an iterator to ensure correct removal. Also tidy up remesh method a bit

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20160 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2260 fix intel build

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20164 b5f69653-2bf5-0310-8201-b0dafb8e1405