Server auth exposes a function to disable pin

[#40]
Pin validator allows blank pin on login

[#40]
Add server endpoint to disable pin

[#40]
Dev UI for disable pin feature

[#40]
Fix border on settings__toggle
Fix box-shadow on main container
Increase width of tab indicator
Fix padding on logout button + replace 'sign out' for 'logout'
Modify _currency on input
Add temp QR button icon
Add some new colours to the auth modal
Switch to numeric keyboard for PIN entry (mobile)
Merge branch 'design/ui-fixes' of github.com:hivewallet/hive-js into design/ui-fixes
Update auth header
Rearrange PIN module
Replace auth header logo (again)
Tidy up + add some style to hive-auth intro