Fixes#1021
A top-right menu item now allows `Account Import`. It has a menu (with one item for now) that allows importing a private key string.
Errors are displayed, and a success navigates the user to their account list, where the imported account is labeled `LOOSE`.
Now old vaults are recognized as an "Initialized" MetaMask instance.
Upon logging in, when fetching the initial password-derived key, if there is no new-style vault, but there is an old style vault, it is migrated to the new format before proceeding through the usual unlocking steps.
- Deleted some unused items
- Renamed files and paths to match with new locations.
- Modified keyring controller logic to separate concerns.
- Fix account naming issues.
- Enable creation of new vault with default HD keyring.
- Formatting issues.