Add support for id, system, and scope attribute on annotation elements

Resolves #335

src/test/resources/eml-with-annotations-with-ids.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<eml:eml packageId="test.1.4" system="KNB"
+         xmlns:eml="eml://ecoinformatics.org/eml-2.2.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="eml://ecoinformatics.org/eml-2.2.0 eml.xsd">
+  <dataset id="hi">
+    <title>Sample datset Description</title>
+    <creator id="23445" scope="document">
+      <individualName>
+        <surName>Smith</surName>
+      </individualName>
+    </creator>
+    <!-- Annotations can have id, system, and scope set on them -->
+    <annotation id="myanno" system="earth" scope="document">
+        <propertyURI label="Subject">http://purl.org/dc/elements/1.1/subject</propertyURI>
+        <valueURI label="grassland biome">http://purl.obolibrary.org/obo/ENVO_01000177</valueURI>
+    </annotation>
+    <contact id="b">
+      <individualName>
+        <surName>Johnson</surName>
+      </individualName>
+    </contact>
+    <contact>
+      <references>23445</references>
+    </contact>
+  </dataset>
+</eml:eml>

xsd/eml-semantics.xsd

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:doc="eml://ecoinformatics.org/documentation-2.2.0" xmlns="eml://ecoinformatics.org/semantics-2.2.0" targetNamespace="eml://ecoinformatics.org/semantics-2.2.0">
+<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:doc="eml://ecoinformatics.org/documentation-2.2.0" xmlns="eml://ecoinformatics.org/semantics-2.2.0" xmlns:res="eml://ecoinformatics.org/resource-2.2.0" targetNamespace="eml://ecoinformatics.org/semantics-2.2.0">
   <xs:import namespace="eml://ecoinformatics.org/documentation-2.2.0" schemaLocation="eml-documentation.xsd"/>
+  <xs:import namespace="eml://ecoinformatics.org/resource-2.2.0" schemaLocation="eml-resource.xsd"/>
   <xs:annotation>
     <xs:documentation>
     Copyright: 2017 Regents of the University of California
@@ -210,6 +211,9 @@
           </xs:complexType>
         </xs:element>
     </xs:sequence>
+    <xs:attribute name="id" type="res:IDType" use="optional"/>
+    <xs:attribute name="system" type="res:SystemType" use="optional"/>
+    <xs:attribute name="scope" type="res:ScopeType" use="optional" default="document"/>
   </xs:complexType>
   <xs:element name="annotation" type="SemanticAnnotation">
     <xs:annotation>