We have been discussing about this merge for a while.
Its main goal is to simplify things: code navigation, but also
packaging.

The rationale is that the code is more cohesive in this way, and there's
only one source package to install.

Dependencies that are only for the server or the client will not be
installed by default, and they are expected to be provided by the
environment. There are setuptools extras defined for the client and the
server.

Debianization is still expected to split the single source package into
3 binaries.

Another avantage is that the documentation can now install a single
package with a single step, and therefore include the docstrings into
the generated docs.

- Resolves: #8896

modifying original PR [0] by cristoph to account for the recent
vendoring of l2db code, which means we no longer depend on u1db/dirspec.

I expect the whole mess about the venv setup to be further simplified
pretty soon, since we are going to merge most of the leap.* packages
into a couple of repos.

[0] https://github.com/leapcode/soledad/pull/327

From this moment on, we embed a fork of u1db called l2db.

Old versions of pip do not accept the --trusted-host option and will complain
when trying to upgrade pip from wheel. To fix that we upgrade pip from usual
location instead of doing it from wheel.