modified_lio_sam

this project based on lio-sam, and modified several items:

1. gps input. now can easily accept raw gns LLA data, and use geography lib to trans data;
2. bag data input. now can use bag.open method to input data, avoid using bag play method;
3. change save strategy, output is more available for users;
4. change some params and method, not significant, just noticed.