[android] add support for schuko/type-E charge sockets

The commit is slightly more complicated that expected because:

- it adds supports for both schuko and type-E, using the same icon (but
  maintaining the underlying type annotated in OSM)

- it adds logic to *not* display the power of schuko socket as 'unknown'
  when not provided in OSM, as it is 'implicit' (3.7kW in most
  countries)

Signed-off-by: Séverin Lemaignan <severin@guakamole.org>

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