RfE: Allow to execute remote commands with jx rsh

[ascheman]

Summary

The command rsh should work like ssh or rsh and execute a remote command.

Expected behavior

Run commands in the target Pod/Container with a command jx rsh -e 'mvn clean compile'.

I have already prepared a prototype implementation. It is necessary to provide the full command in quotes.

An alternative could be to append arbitrary commands with a double dash (--).

[ascheman]

Thanks for merging!