Data cleanup

[tzussman]

• Remove get_hydrobasins.py and get_merit_dem.py scripts, as this functionality is available in rabpro and in the CLI
• ~Remove the Data/HydroBasins and Data/MERIT_Hydro directories, as these are no longer used and can be created in the appropriate location both in rabpro and the CLI~
• ~Remove Data files from .gitignore~

I wanted to rename the directory from Data to data, but we have hardcoded URLs which require the Data form... Unfortunate, but not worth breaking anything over this

[jsta]

I liked having the Data directory as an example of the structure expected by rabpro but I'll defer to the will of the community.

[jonschwenk]

I think I'm with @jsta on keeping the Data subdirectories. Many of our potential users will appreciate all the examples they can get...@tzussman can you roll those back and resubmit?

[tzussman]

Yep, will do!

[tzussman]

@jonschwenk @jsta ready for re-review