Create a "fare type" for cargo

[nabeelio]

Allow changing a fare type to passenger or cargo. Cargo flights would be language change mainly; price being the amount charged per pound, and capacity being a max amount in lbs, since it's assigned to a subfleet.

Keeping it this way will allow for mixed cargo/pax flights, since fares can be assigned to subfleets accordingly. Upon selecting a subfleet/aircraft, the fares dropdown will still show applicable fares, just that cargo is now an option without hacks.

• Create a new FareType enum - cargo or pax
• Change the language in adding fares
• Indicate in fare tables whether its cargo or pax
• Language in finances and separate ledger rows for pax and cargo