- All conversions to CSR (except CSR to CSR) now conserve the original
  strategy (test for that are included)
- CSR strategies now try to copy the least amount of data
- Add exception throwing in case the load_balance would not work
  properly (when srow is empty)

- Make strategy helper variables const to ensure they do not change
- Fix Hybrid read function

- GKO_NOT_SUPPORTED is the only macro that does not include the
  `throw`. This was not only a problem in this code, but also in
  unrelated code, which is also fixed within this commit
- An Empty Dense matrix can now be converted to a CSR matrix
- Moved the `GKO_NOT_SUPPORTED` to the cuda kernel, so empty matrices
  do not throw when applying a strategy.

- Change a `static_cast` in the strategies to a constructor call
- Move empty matrix test from CSR to Dense (and add a move test)

`update_ginkgo_header.sh` now no longer returns a non-zero exit code,
meaning it should no longer stop the `make` process when something
goes wrong or is not found.
Additionally, the script is now only called if `GINKGO_DEVEL_TOOLS` are
enabled since non-developer would not benefit or need it.

- Add additional tests for access privileges
- Add `rm` parameter

Changed `rm` parameter to `-f` in order to have a wider OS support.