.ini: Changed sqlalchemy.url prefix to postgresql://

postgres:// is deprecated
tests/lib: Added unittest for skylines.lib.base36
lib/base36: Simplified method names
lib/formatter/flight: Moved code into Jinja2 template for better i18n
templates/tracking: Removed unused/empty block
templates: Added user_link/club_link macros
templates/macros: Added airport_link macro
i18n: Updated .pot file