add dc:source for description of platforms and instruments, and revise descriptions accordingly. Remove thesauri for single Collections as they are all included in the mmd-vocabulary files., change path for picking up vocabulary in dif-to-mmd. Fix few typos.
closes #152
add dc:source for description of platforms and instruments, and revise descriptions accordingly. Remove thesauri for single Collections as they are all included in the mmd-vocabulary files., change path for picking up vocabulary in dif-to-mmd. Fix few typos. closes #152