Revisit code style for tool / CredentialStoreCommand

This should probably wait until after ELY-1842 as refactoring before will cause more problems.

Working on ELY-1842 another engineer has also worked on an RFE for different reasons to adjust the credential store, the current code has a long method building up with the options for the command line - if multiple engineers work on this code it leads to conflicts easily but is also hard to unravel to correct the conflicts.

As the scope of CredentialStoreCommand has expanded since it's original implementation which was very tightly constrained we probably need to break this up into more logical chunks, also many variables just have a very short name which keeps the code concise but if you have not bee in the code for a while it is hard to see the purpose of each variable to we should expand the variable names to be more meaningful.