Make the PyPI distribution name consistent with the domain name and debian packages.

[nejucomo]

Criteria:

This ticket is closed when the PyPI package name is tahoe-lafs, otherwise this ticket is set to a different unopen status.

Synopsis:

The distribution names are inconsistent, as seen in: ​https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1950#comment:6

• PyPI package name is {{{allmydata-tahoe}}
• The debian name is tahoe-lafs
• The domain name is tahoe-lafs.org: ​https://tahoe-lafs.org
• The github name is tahoe-lafs: ​https://github.com/tahoe-lafs/
• Anecdotally the common "spoken name" is either "tahoe" or "tahoe lafs".

I propose we alter the PyPI package to match the others: tahoe-lafs

Related:

• #1950 is about a larger, more time consuming project which involves changing the python module names as well.