docker: Elasticsearch catchup
docker: Elasticsearch catchup

* BETTER Adds Elasticsearch container and adds configuration for
  Elasticsearch search hosts called `ES_HOSTS`.

* Adds `invenio-records` as a requirement.

* Disables some tests which are using `httpretty`. The monkey patching
  used by this library leads to failures in some cases, which are
  difficult to reproduce. It mostly seems to affect the connection
  handling (which makes valid assumptions about how sockets work) of
  elasticsearch. An upgrade of `httpretty` did not lead to a fix.
  We might want to change to a more stable HTTP mocking system.

* BETTER Improves parts of the Docker documentation.

* INCOMPATIBLE Upgrades the general `requests` library minimal
  requirement in Invenio to version 2.4. This will lead to the usage
  of `keep-alive` in most cases. Elasticsearch uses this to improve
  efficiency.

* INCOMPATIBLE Switches from hard-coded Redis host to ENV based
  configuration for Docker.

Signed-off-by: Marco Neumann <3829486b93ec44395f0b980424bae9b6fb07b7bc@crepererum.net>

tiborsimko/invenio-access,inveniosoftware/invenio-access,tiborsimko/invenio-access,inveniosoftware/invenio-access