Make CLEASE independent of lattice constant

We currently have to use the same lattice constant for all structures that are used (@davidkleiven can you confirm?). If so, it would be nice to make CLEASE independent of the lattice constant such that one can import structures from several CE projects without having to change the lattice constant of the initial structure to match. It is quite straightforward for structures like FCC, BCC, SC. For more general cases with more than one constants (e.g., HCP) and other spacegroups, my hunch is that everything will be fine so long as we enforce the structures to have the same basis (scaled coordinates).

Any suggestions?