*v1: no deletion, one directory per verifierid, one owner per share,
leases never expire
v2: multiple shares per verifierid [zooko]
+ v2.5: deletion
v2: leases expire, delete expired data on demand, multiple owners per share
UI: (brian)
webish? webfront? PB + CLI tool? FUSE?
*v1: readonly webish (nevow, URLs are filepaths)
-*v2: read/write webish
+*v2: read/write webish, mkdir, del (files)
+ v2.5: del (directories)
v3: PB+CLI tool
v4: FUSE