Make colmapDataParser compatible with 360_v2 dataset format

[Jing1Ling]

In order to be compatible with the original format of the 360_v2 dataset without reprocessing it, I added an option to colmapDataParser to round up the image size when downscaling. This may change the image height and width in the camera. But I'm not sure if it will have any negative impact on other parts? If so, please let me know. Thank you!