Add test for Berlin harvester sector amendment

Just added a unit test to check whether the sector is set if not
provided by the Berlin open data portal.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Extend sector amendment test and implement patch

I have extended the unit test for the Berlin harvester's sector
amendment. This commit also implements the sector amendment.

From now on, the method amend_package should return a Boolean which
indicates whether the package is valid or not. In the latter case the
package is dropped. This way the code is a lot more testable.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Add missing test case for sector amendment and fix

I have forgotten one case in the sector amendment: if the sector key is
present but its value is set to None the sector is not set to the value
'oeffentlich'. Hence, I have added another test case which covers this
and also added a fix.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Add test and fix for Berlin package type amendment

Since there are two documents in the Berlin datasets and in order to
make the amendment more robust against further documents or app the
harvester code is changed. Now the type is only set if its None to
default value 'datensatz'.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Add additional case if the set type is invalid

I have forgotten the case if the package type is set by the data
provider but not to a valid type: not an element of ['datensatz',
'dokument', app']. This commit fixes that.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Change metadata original portal amendment

Similar to the commits before the metadata original portal amendment is
adjusted as well. If field is already set it is left, otherwise it will
be set to the default value 'http://datenregister.berlin.de'.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>