Cli fs operations refactoring

[azazel]

Actually, almost each of the cli commands implement their own logic to do fs operations, both local-side and tahoe-side. I think that most of the command modules should be refactored to use common code. This is for many reasons among:

• remove duplication;
• code comprehensibility and normalization of behavior;
• spread avaiability of improvements found in latter commands (backup) to other commands;
• easier implementation of new features like non-ascii charset handling for filenames;
• better handling of logging?

The steps in order to do that (that i can see):

1. Recognize the needs of each command in term of fs manipulation;

2. Look at the best implementation available and eventually improve it;

3. maybe design a minimal layer that will help handling alias/path/cap based opetations and other cases.

Other interesting points to discuss:

• See if a replacement of httplib with twisted can help in parallelizing and increasing the bandwidth usage.

Let's discuss it!