Crabpy-pyramid

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- Add HTTP caching headers. Both conditional GET with ETags and Cache-Control
headers. Caching times are based on the ones passed to the gateways. (37)
- Empty proxy settings are filtered out before being passed to the gateways. (38)

- Exposes CRAB and CAPAKEY gateways.
- CRAB Gateway also exposes some Provincie objects. (13)
- CRAB and CAPAKEy can be configured independently. (11)

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- Update dependencies. Update pycountry to version 1.19.
- Add explicit support for python 3.5.
- Add deelgemeenten. (33)
- Added postadressen in a few places.
- Added a list of huisnummers to a CRAB perceel.

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- Add Adresposities. Add endpoints that exposes the Adresposities linked to a
certain Huisnummer or Subadres. (26) [TalissaJoly]
- Add Landen (countries). Add endpoints to get a list of Landen or more
information about a single Land. (30, 31) [TalissaJoly]
- Return HTTP 404 errors for certain unexisting resources. (25) [TalissaJoly]
- Limit the number of results that can be returned in a list. There was some
partial handling for this, but only when the user did not send any range
headers. This behavious was deemed potentially hazardous and changed. Now,
only a maximum of 5.000 records will be returned and range slicing works
correctly. (16) [TalissaJoly]

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- Implement two service endpoints dealing with Subadressen (think of boxes
in an appartment building). (18) [TalissaJoly]
- Implement a service endpoint for listing the Postkantons (ie. Postcode) in
a certain gemeente. (23) [TalissaJoly]
- Cleanedthe code a bit by removing unneeded bits and pieces. (17) (19)
[TalissaJoly]

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- Minor release adding and cleaning up lots of service documentation. (14)
- Fixes a small bug when no capakey username or password was set and the capakey
service was included.