addgrader.sh will now run more universally

If you have a signing key and it's already in the repository, it will not do anything.
If you have a signing key and it's not in the repository, it will add the key to the repository.
If you don't have a signing key, it will generate a new key as it did before.

Keys existing in the repository will no longer get overwritten.

Removed key checking from uploadGrades since it will run too many times if uploading many grades at once. Run addGrader.sh to resolve signing key issues instead.

fixed conflicts