Updating tutorials to newest release of pydap

[Mikejmnez]

Latest release of pydap has a new feature: pydap is able to stream in parallel multiple dap responses, and stream them directly into their own netcdf4 file.

This PR:

• Adds new tutorials demonstrating new pydap features
• Updates existing tutorials (earthaccess and virtualizarr)
• Updates the organization of these tutorials. There are 3 ways to use opendap: pure pydap, xarray+pydap, and earthaccess+DMRpp+virtualizarr