Merge pull request #184 from Turbo87/i18n

Updated translations and template
model: Added tracking_callsign column to User model
tracking: Don't show "other pilots" table if it's empty
forms: Added tracking_callsign field to "Edit User" form
templates: Use tracking_callsign if available, otherwise initials
Merge pull request #187 from Turbo87/user-callsigns

User-configurable callsigns for the tracking pages
forms: Removed club field from registration form

This caused much confusion because people didn't know how to add their
own club to the list upon registration so they didn't register. Now we let
them register without a club and discover the proper club change form
later.
Merge pull request #188 from Turbo87/clubless-registration

forms: Removed club field from registration form
views/user: Fixed recover_password() method
model/event: Import cleanup
views: Import cleanup
flake8: Added "# noqa" lines to __init__.py files

Ignore "unused import" warnings in these files
Added flake8 to requirements.txt
setup.cfg: Add project-wide flake8 configuration
tests: Replaced PEP8 test with flake8 test
scripts: Import cleanup
scripts: Added "# noqa" to side-effect imports
Merge pull request #189 from Turbo87/flake8

Flake8 support
macros/flash: Added 'success' message type support
views: Moved /user/.../edit to /settings/profile