installation: PyLD to 0.5.0

* Using inveniosoftware's fork with has a special version number
  26.0.5.0-dev to prevent further updates to override it.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
docs: documentation refactoring

* fixing the images' path.

* removing references to non-existing files.

* moving modules into proper files.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
annotations: sphinx friendly documentation

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
upgrader: sphinx friendly documentation

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>