make the FUSE interface be a supported, first-class feature

[zooko]

In v1.7.0, released on 2010-06-18, we added a fully supported SFTP server (see ​The Parade Of Release Notes). However, there remains a widespread perception that Tahoe-LAFS doesn't have FUSE integration or doesn't have real, well-supported FUSE integration, or that we have several alternative FUSE interfaces, none of which completely works.

Examples:

• ​http://tahoe-lafs.org/pipermail/tahoe-dev/2011-February/006031.html # (see the end of the letter)
• ​http://tahoe-lafs.org/pipermail/tahoe-dev/2011-January/005987.html
• ​http://tahoe-lafs.org/pipermail/tahoe-dev/2011-February/006052.html

To close this ticket you have to do the things on the following list. (You may also need to add to this list or to move some of the things on this list to separate tickets as appropriate.)

• remove the old, unsupported FUSE implementations from source:trunk/contrib/fuse
• consider rescuing source:trunk/contrib/fuse/runtests.py , configuring it to test the current, supported SFTP-based FUSE plugin, program a buildbot to run that test
• document how to install Tahoe-LAFS as a FUSE plugin (can the install process be automated somehow?)
• add to The FAQ a question: "Can I access Tahoe-LAFS through FUSE?" with an appropriate answer
• document somewhere a clear, non-weasel-wordy answer to the question of whether the reader should use the SFTP-based FUSE plugin or the PyFilesystem-based FUSE plugin. (For one thing, the former is supported by the Tahoe-LAFS team, which means it was developed by a brilliant coder -- David-Sarah -- under full test driven development, and is subject to our practices intended to promote security, stability, and backward-compatibility.)
• ? document somewhere what are the important differences between the WUI, CLI, and FUSE interfaces