Validate character set for BICs

[raphaelm]

Hi,

we've noted that a lot of our users try to input spaces into the BIC field and then run into the maxlength attribute silently. For example, if they want to input DEUTDEFFXXX, they end up inputting DEUTDEFF XX. As I understand SWIFT, all BICs are alphanumeric, even the branch codes. Therefore, I suggest

• validating that all BICs only contain letters and numbers.

• auto-removing spaces from form input

• 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.´

[codecov-io]

Codecov Report

Merging #364 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #364      +/-   ##
==========================================
+ Coverage   95.93%   95.93%   +<.01%     
==========================================
  Files         157      157              
  Lines        3981     3983       +2     
  Branches      523      524       +1     
==========================================
+ Hits         3819     3821       +2     
  Misses         98       98              
  Partials       64       64

Impacted Files	Coverage Δ
localflavor/generic/forms.py	100% <100%> (ø)	⬆️
localflavor/generic/validators.py	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 00fe4ec...0eca782. Read the comment docs.

[benkonrath]

Thanks for your contribution and for providing valuable insight into the problem that some users were running into with the validation. The PR looks good!