Anonymous mode fails in Firefox private mode

[ivandotv]

Since anonymous mode depends on IndexedDB it fails in Firefox private mode ( IDB is disabled in FF private mode).

[ivandotv]

Possible solution:
step 1: Detect error when opening IndexedDB, and notify the user.
step 2: Switch to simple in-memory storage, which will be lost when the user closes the window, and that's okay since that is expected when using private mode.

fake indexeddb can be used for 1 to 1 in-memory mapping of IndexedDB API.