Revise database directory structure

[hackergrrl]

Our current disk layout is:

0/
1/
2/
...
media/
storage/
index/

I propose the following:

feeds/    <--- has 0/, 1/, 2/, etc
media/   <--- same
indexes/
--- views/   <--- used to be index/ (has all kappa view leveldbs)
--- raw/  <--- used to be storage/ (has all binary data like the bkd tree)

This will make it much easier to

• download a subset of the data from the Google Drive interface
• wipe the indexes

Open question: how will we change over existing devices? They'd need to detect the old layout and do a rename in bulk, or we support the legacy format when the new directories aren't found, but prefer to use the new layout for new devices.

[hackergrrl]

cc @gmaclennan @okdistribute

[gmaclennan]

This makes sense to me. I think prior to initialization, checking for the old format somehow and moving directories would be best, then the bulk of the code does not have to worry about legacy format support.

[okdistribute]

+1 on this!