Add a more flexible type system (e.g. for MAGMA)
Support for MAGMA LAPACK backend
Fix issues related to MAGMA integration
Add one init() routine for all GPU libraries
Fix bug in Dense.reallocate() on the GPU
Improve error messages for metadata

Made the wording more clear, added routines to convert types to strings
to allow for more concise error messages.
Remove cruft that accidentally got committed
Fix usage of cublasXgeam in copy_2Darray()
Fix various smaller things and add TODO comments