Use HANA Cloud Platform API jar from Maven central

- Use a more recent version of the HANA Cloud Platform API jar which
  is available from Maven central.
- Drop manual upload of the API jar to the local Maven repository, which
  is no longer needed.
Add missing settings.xml configuration in README.md

- In order to build the project, one needs to configure Maven so that
  it has access to the Jenkins Maven repository. In a non-corporate
  environment, this is done by adding the repository in a profile in
  the settins.xml.
Various README.md improvements

- Adapted to changes of labels in the HANA Cloud Cockpit.
- Replaced proxy configuration by a link (because the existing
  instructions were incomplete; they didn't work on Windows)
- Consistent formatting and indentation.