Part of #2455 - Private browsing mode and TOR-browser

When i run bitshares-ui in the TOR-browser(based on Firefox 60.4.0esr) or in private mode in Firefox 64.0, it scans available nodes and stops after that with error "DOMException: A mutation operation was attempted on a database that did not allow mutations."
Perhaps it happens because of inaccessibility of the indexedDB (Context: IndexedDB doesn't work in private browsing mode https://bugzilla.mozilla.org/show_bug.cgi?id=781982)


The issue names no source files, tests, or entry points. First reproduce the failure in Firefox private mode or the TOR browser and trace the IndexedDB initialization and node-scanning flow; done means the application handles unavailable IndexedDB without stopping after scanning nodes, with regression coverage for the affected mode.

Written by the indexing model from the issue text.