Add area lable fix V2

[marionb]

This is a second version that fixes #96 A fist one was done in #104

To test set the parameter display_real_estate_subunit_of_land_register in the config of pyramid_oereb to False.

@michmuel can you take a look at this and tell me if this works for you? We still have duplicate code but I am separating it so that it is more readable and reflects what we have already done in other places.

Note this would also close #104

[jwkaltz]

Thanks for the review @michmuel , so https://github.com/openoereb/pyramid_oereb_mfp/pull/104 can be closed, is that correct?