Add DummyRunner.

The PanelRunner is now a based on a generic ICommandRunner class that executes and parses a command. The command itself is built in inherited classes by the command function.

There are two inherited classes. PowertoolsRunner that builds up a pbv3_mass_test command string on the local (or remote) computer. This is the same as the previous PanelRunner. The second is DummyRunner that is configured using a logfile path containing the results of a previous pbv3_mass_test and just outputs the contents using the cat command. This can be used for local development of the GUI.