Android: Don't create a certificate if the alias field is empty.

We need to make sure that the user fills in the alias field before we
generate the certificate. If the certificate does not have an alias,
the package creation step will only create debug packages.

Task-number: QTCREATORBUG-10050
Change-Id: I247c7218a55ec86bdb1408c90f7f403b2ebbe2a4
Reviewed-by: BogDan Vatra <bogdan@kde.org>
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Android: Improve the Keystore and Certificate dialog.

- Display all information in one place.
- Checkbox to enable the certificate to use the same password as the
  Keystore.
- Display information when alias field is empty.
- Misc. layout changes.

Task-number: QTCREATORBUG-10061
Change-Id: I99a3e7019dfbf72bcd2374594f3ebe45c26680d2
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: BogDan Vatra <bogdan@kde.org>