Fix the dial string to include the + sign added by user for VT call

- The smart dial search normalizes the dial string and removes
  anything other than digits

- Add a fix to add the + sign back to the normalized string
  if original typed number had a + sign

- Add a check for prohibited numbers before making a call
  and display an error dialog

Change-Id: Ib36462be573ce4fecc8821980226ae2920041cd2