Revert "Stop creating per-user databases. Closes #4626."

This reverts commit 6eeed5c116d38ebae7d9309dd2f11660f6cff37e.
Revert "Remove creation of shared database from soledad server code. Closes #4566."

This reverts commit eb07702bc4c1d51e0307b655b14bc1a3835488b2.
Merge remote-tracking branch 'chiiph/bug/revert_database_creation' into develop