[qtcontacts-sqlite] Skip invalid alphabetic characters in phone numbers

Alphabetic characters in the DMTF character set are only valid if they
occur after some numeric component of the number.  If they occur
prior to any numeric component, they should be skipped in normalization.

This is to prevent non-number input such as 'Plumber' being normalized
into 'P'.
Merge pull request #142 from matthewvogt/invalid-alpha-chars

[qtcontacts-sqlite] Skip invalid alphabetic characters in phone numbers