add 'Tahoe Explorer' (JavaScript-based UI) to Tahoe

[davidsarah]

Toby Murray ​has written a JavaScript front-end called "Tahoe Explorer", which looks very promising -- particularly from the point of view of solving security problems with the existing WUI, as well as potentially better usability and performance. (It's not often you get to improve all of those at the same time!)

I don't think this should be added just as a 'contrib' package; it is liable to bitrot that way.

The original code was dependent on Cajita, which would have required solving some (minor) licensing issues, but it turns out that this dependency is easily removed.

Of more concern is that the code has no unit tests. We need to decide how to test JavaScript code (there are several possibilities including ​JSUnit and ​Windmill; I'll open another ticket about that).

[duck]

Toby Murray's Tahoe Explorer