Work on enabling PTY operations

[rhc54]

Provide a cmd line option to specify the user wants to spawn a PTY - e.g., to run a shell on a remote node. Correct error code returns when pipes don't properly get setup, and add an error log so we can see where that happens.

When using PTYs, setup all standard IO file descriptors as pty's. Set their term attributes and window sizes to match those of the user's endpoint (i.e., prterun or prun).