added script (downloader_msg_modis_overpass) to download msg timestamps whenever MODIS has an overpass. Note that an equivalent script does not yet exist for GOES
changed try/except loop in msg download.py to avoid the program from crashing when no product or file is found. With this, I was able to download data for all of 2010
added functionality to add either specific timestamps, or date/time ranges to GOES and MSG download.py. This way, it's easier for the users to query specific data (for instance with MODIS overpasses)
added scripts to download MSG data in monthly chuncks. Even with some refactoring, the download is very slow, so it's better to parallelize.
Overview of changes: