Austrian mobile numbers can have 7-10 digits in the subscriber number

As listed in the table on page 17 of the Austrian ITU document https://www.rtr.at/en/tk/E129/2312_Austrian_Numbering_Plan_2011-03-30.pdf
a mobile number can be between 7 and 10 digits in the subscriber number. This is also something we noticed with some of our customers
as well.
Merge pull request #202 from tpena/enhancement/Austria-mobile-length

Austrian mobile numbers can have 7-10 digits in the subscriber number