uses-permission maxSdkVersion as int, and enforces int string in XML

uses-permission maxSdkVersion as int, and enforces int string in XML

This forces <uses-permission maxSdkVersion=""> to be an integer in the
internal dict, and forces it to have no decimal point in XML.  Having it as
an integer in the internal dict means data will pass directly through to
the fdroidclient Apk instance, where it is ultimately an integer.