Added 23 new/modified files. Changed file names to go with new order.

Ediited Complete.json mapping and added a file log to track file modifications to the original English subtitles. New files include:

 1. 02a-Simple_Aggregation_Example-Lecture
 2. 03a-The_Aggregation_Pipeline-Lecture
 3. 05a-Multikey_Indexes-Lecture
 4. 07-Installing_MongoDB_mac-Lecture
 5. 09a-Index_creation_options_sparse-Lecture
 6. 09b-Index_creation_options_sparse-Answer
 7. 11-Multikeys-Lecture
 8. 15-Hello_World_on_a_Web_Server-Lecture
 9. 15a-Using_$match-Lecture
 10. 16-Mongo_is_Schemaless-Lecture
 11. 16a-Using_$text-Lecture
 12. 16b-Using_$text-Answer
 13. 20a-Geospatial_Spherical-Lecture
 14. 20b-Geospatial_Spherical-Answer
 15. 21a-Text_Searches_in_MongoDB-Lecture
 16. 21b-Text_Searches_in_MongoDB-Answer
 17. 23-Using_$out-Lecture
 18. 24a-Aggregation_Options-Lecture
 19. 24b-Aggregation_Options-Answer
 20. 25a-Python_and_Aggregation_Results-Lecture
 21. 25b-Python_and_Aggregation_Results-Answer
 22. 26-getLastError-Lecture
 23. 28-Limitations_of_Aggregation_Framework-Lecture