Add disclaimer that "Tahoe-LAFS is unrelated to Tahoe Data Manager" and petition TDM publisher to add similar disclaimer.

[nejucomo]

Synopsis:

There's a potential naming confusion with the "Tahoe Data Manager" Firefox Addon:

​https://addons.mozilla.org/en-US/firefox/addon/data-manager/

Criteria:

Close this ticket when:

• Either:
  • The front page at ​https://tahoe-lafs.org disclaims "Tahoe Data Manager" is unrelated, and:
  • We contact the author of "Tahoe Data Manager" requesting the same type of disclaimer on the Addon description.
• or:
  • We believe the potential confusion will not be widespread.