make bom.version a positive integer, was integer

Signed-off-by: Jan Kowalleck <jan.kowalleck@gmail.com>

Author: jkowalleck

schema/bom-1.5.schema.json

@@ -42,6 +42,7 @@
       "type": "integer",
       "title": "BOM Version",
       "description": "Whenever an existing BOM is modified, either manually or through automated processes, the version of the BOM SHOULD be incremented by 1. When a system is presented with multiple BOMs with identical serial numbers, the system SHOULD use the most recent version of the BOM. The default version is '1'.",
+      "minimum": 1,
       "default": 1,
       "examples": [1]
     },

schema/bom-1.5.xsd

@@ -4100,7 +4100,7 @@ limitations under the License.
                     </xs:annotation>
                 </xs:any>
             </xs:sequence>
-            <xs:attribute name="version" type="xs:integer" default="1">
+            <xs:attribute name="version" type="xs:positiveInteger" default="1">
                 <xs:annotation>
                     <xs:documentation>Whenever an existing BOM is modified, either manually or through automated
                         processes, the version of the BOM SHOULD be incremented by 1. When a system is presented with