Fix xsd inconsistences with OTA
Our XSD file is missing some restrictions that OTA defines. Since AlpineBits in general is more strict than OTA, this can be considered as a bug.
In this case we define a non empty string object which is used pretty often. Meanwhile OTA for the same elements has a maximum string length of 8, 16, 32 etc.
<xs:simpleType name="def_nonempty_string">
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
</xs:restriction>
</xs:simpleType>
This has to be verified not only for the strings but for all objects. Then the schema file has to be updated and adjusted.