Adapted Slovenian rule matching based on ITU and Twiki info

Page 1 of the ITU document http://www.itu.int/oth/default.aspx?lang=en&parent=T02020000BE indicates the
possible structures of the National (Significant) Numbers. We used this information, with the focus on
mobile numbers, to fix up the parsing rules. Furthermore, the maximum length of the NSN is 8 digits whic
meant that the previous parsing rule (fixed(2) >> split(3, 2, 2)) would not return the correct plausibility
results for valid numbers.

Added plausibility as well as formatting specs.
Merge pull request #201 from tpena/enhancement/Slovenia-number-length

Adapted Slovenian rule matching based on ITU and Twiki info