Throw Exception
Fix Tests
Update example(PDO)
Merge remote-tracking branch 'shield9/throw-exception'

Conflicts:
	src/u2flib_server/U2F.php
add an override to the Error constructor

making message and code mandatory
switch test to use annotations for exceptions

and adding annotation for the error code, drop commented out assertions
update apigen comments for exceptions
update localstorage example for exceptions