update docs for 1.10 release

NEWS: caution about secret introducer.furl in world-readable tahoe.cfg

known_issues, quickstart: add version and anticipated release date

update deps URLs to use "tahoe-lafs" instead of bare "tahoe"

whitespace change to trigger buildbot for 1.10-b1

NEWS: add unsorted recent entries. I think that's all of them.

This list includes the changes made between 1.9.0 and the 1.9.2 darcs
release. There are also lots of non-user-visible changes, but NEWS
doesn't need to include them.

Makefile: re-enable tarball uploads for "master" branch

.gitignore: also ignore tahoe-deps and .tgz, to fix 'make tarballs'

Otherwise, the get-version-from-git code thinks the tree is dirty, and
creates SUMO tarballs with -dirty in the name.

TAG allmydata-tahoe-1.9.0

TAG allmydata-tahoe-1.9.0b1