Integrate VPN with new keystore and misc fixes.

* Changes
  + Pass intent to keystore when needed and hooks to resume from it.
  + Generate random, unique ID for profile instead of base64 from its
    name.
  + Add VPN to "Wirless controls" description.
  + Add credential storage to "Security & location" description.
  + More hints to set password and unlock dialogs in credential storage
    settings for actions that come from other processes.
  + Sort VPN profiles according to the names.
  + Replace Keystore with CertTool in L2tpIpsecEditor