[sugar] adding versions to journal/datastore

[Marco Pesenti Gritti]

I suggest that we proceed as following:

1 Next week we are planning to land Tomeu datastore rewrite. It's a
drop in replacement with no API changes, which should allow us to have
a solid, simple datastore in 0.84 and to start working on all the the
small, but fundamental UI improvements which we delayed in the last
year waiting for perfect DS to show up. (better automatic tagging by
activities, encourage to title entries, fine scrolling view, open the
last document by default when launching activities, performance
improvements and a bunch of other cool stuff).

2 Scott, Erik, Tomeu, Michael, Chris (am I missing anyone? :P) are all
racing to design a more powerful datastore which would provide
versions, advanced tagging and better compatibility with POSIX. I'm
particularly excited about the possibility to collaborate with GNOME
on it, it would be a great sinergy: looking forward for the result of
the summit! These efforts are more invasive, still being researched,
and will likely require API changes. We should encourage them, give
them enough time to mature and to reach consensus inside the
community. The "winner" should land when it's ready and compatibly
with the project schedule. In particular, the deadline for new modules
proposal is at the end of the week.

Marco