Avoid trying to start web worker client in crypto_worker.js outside of web worker context
Remove crypto_worker.js <script> preload

This is no longer needed as the web workers are initialized when
the web app loads.
Display a label on the unlock pane to indicate the unlock state
Add ItemContent functions to retrieve primary account name and password for item

Add utility functions to retrieve the main account name / password
for the item.

The exact field that this maps to will depend on the item type.
For logins it maps to the form fields with 'username' and 'password'
as the designation.
Initial cut of item details view

Currently displays icon, item title, item account and password
plus a link to go back to the main item list.