Ie model fields

[paulcunnane]

This change adds an "EircodeField" to the Irish local flavour. An Eircode is
an Irish postcode (https://www.eircode.ie). The format of the Eircode is
validated, but its existence is not.

Thanks for your contribution!

A checklist is included below which helps us keep the code contributions
consistent and helps speed up the review process. You can add additional
commits to your pull request if you haven't met all of these points on your
first version.

All Changes

• Add an entry to the docs/changelog.rst describing the change.

• Add an entry for your name in the docs/authors.rst file if it's not
  already there.

• Adjust your imports to a standard form by running this command:

  `isort --recursive --line-width 120 localflavor tests`
  

New Fields Only

• Prefix the country code to all fields.

  I haven't done this, because "Eircode" is a uniquely Irish name for
  a postcode.
  

• Field names should be easily understood by developers from the target
  localflavor country. This means that English translations are usually
  not the best name unless it's for something standard like postal code,
  tax / VAT ID etc.

• Prefer 'PostalCodeField' for postal codes as it's
  international English; ZipCode is a term specific to the United
  States postal system.

  Again, it's called "Eircode" because we just don't call them postal codes.
  

• Add meaningful tests. 100% test coverage is not required but all
  validation edge cases should be covered.

• Add documentation for all fields.

[benkonrath]

Thanks for your contribution. Can you rebase this branch with master? That will pickup the latest changes and fixes to the CI config and the tests should pass. I'll do the review once you've rebased. Thanks.

[paulcunnane]

I think that's done now (not a git expert!)

[codecov-io]

Codecov Report

Merging #360 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #360      +/-   ##
==========================================
+ Coverage   95.93%   95.94%   +0.01%     
==========================================
  Files         157      157              
  Lines        3981     3996      +15     
  Branches      523      525       +2     
==========================================
+ Hits         3819     3834      +15     
  Misses         98       98              
  Partials       64       64

Impacted Files	Coverage Δ
localflavor/generic/validators.py	100% <ø> (ø)	⬆️
localflavor/ie/forms.py	100% <100%> (ø)	⬆️
localflavor/no/forms.py	87.35% <100%> (ø)	⬆️

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