Updated Values, Added Varients, and prod dates

TU-204-100 Updated performance
TU-204-120 Slightly improved fuel efficiency(hey, every drop counts in this world)
TU-204-300 updated performance
Updated info from sources such as
http://www.airlines-inform.com/commercial-aircraft/
http://www.aviastar-sp.ru/en/products_and_services/aircraft/tupolev_204_300/
Also reworked some math as it was designed similar to the 757, just a bit less competitive.
Not all Russian planes are fuel hogs :) Based on my homework, I feel that these numbers properly match the planes's design and performance capabilities
Merge pull request #276 from Technotron3/patch-1

Updated Values, Added Varients, and prod dates