tsm-client: init at 8.1.8.0

IBM Spectrum Protect (former name: Tivoli Storage Manager)
provides a single point of control for backup and recovery.
This package contains the client software, that is,
a command line client and linkable libraries.

This commit adds two packages to nixpkgs:
The TSM client software contains a Java GUI
that, naturally, requires Java to be installed.
To keep the closure size low, we provide the packages
`tsm-client` and `tsm-client-withGUI`.
The former comes without the Java GUI.

While the product has been renamed, its old name is still
alive in filenames and as package name used by other distros.