Fix tool XSD to document <conversion> tag for data parameters.

Rebased with English fixes and small tool cleanups thanks to @nsoranzo.

doc/schema_template.md

@@ -25,6 +25,7 @@ $tag:tool|inputs|conditional|when://complexType[@name='ConditionalWhen']
 $tag:tool|inputs|param://complexType[@name='Param']
 $tag:tool|inputs|param|validator://complexType[@name='Validator']
 $tag:tool|inputs|param|option://complexType[@name='ParamOption']
+$tag:tool|inputs|param|conversion://complexType[@name='ParamConversion']
 $tag:tool|inputs|param|options://complexType[@name='ParamOptions']
 $tag:tool|inputs|param|options|column://complexType[@name='Column']
 $tag:tool|inputs|param|options|filter://complexType[@name='Filter']

lib/galaxy/tools/xsd/galaxy.xsd

@@ -2338,6 +2338,7 @@ allow access to Python code to generate options for a select list. See
           <xs:documentation xml:lang="en">Documentation for label</xs:documentation>
         </xs:annotation>
       </xs:element>
+      <xs:element name="conversion" type="ParamConversion" />
       <xs:element name="option" type="ParamOption" />
       <xs:element name="options" type="ParamOptions"/>
       <xs:element name="validator" type="Validator" />
@@ -2638,6 +2639,32 @@ if the corresponding option is selected by default (the default is ``false``).
     </xs:simpleContent>
   </xs:complexType>
 
+  <xs:complexType name="ParamConversion">
+    <xs:annotation>
+      <xs:documentation xml:lang="en"><![CDATA[
+
+A contrived example of a tool that uses this is the test tool
+[explicit_conversion.xml](https://github.com/galaxyproject/galaxy/blob/dev/test/functional/tools/explicit_conversion.xml).
+
+This directive is optionally contained within the ``<param>`` tag when the
+``type`` attribute value is ``data`` and is used to dynamically generated a converted
+dataset for the contained input of the type specified using the ``type`` tag.
+
+]]>
+</xs:documentation>
+    </xs:annotation>
+    <xs:attribute name="name" type="xs:string">
+      <xs:annotation>
+        <xs:documentation xml:lang="en">Name of cheetah variable to create for converted dataset.</xs:documentation>
+      </xs:annotation>
+    </xs:attribute>
+    <xs:attribute name="type" type="xs:string">
+      <xs:annotation>
+        <xs:documentation xml:lang="en">The short extension describing the datatype to convert to - Galaxy must have a datatype converter from the parent input's type to this.</xs:documentation>
+      </xs:annotation>
+    </xs:attribute>
+  </xs:complexType>
+
 
   <xs:complexType name="ParamOptions">
     <xs:annotation>

test/functional/tools/explicit_conversion.xml

@@ -11,10 +11,8 @@
     <data name="output1" format="tabular" from_work_dir="col_output" />
   </outputs>
   <tests>
-    <!-- Test implicit conversion. -->
     <test>
       <param name="input1" value="1.fasta" ftype="fasta" />
-      <param name="col" value="1" />
       <output name="output1">
         <assert_contents>
           <has_line line="hg17" />

test/functional/tools/implicit_conversion.xml

@@ -12,7 +12,6 @@
     <!-- Test implicit conversion. -->
     <test>
       <param name="input1" value="1.fasta" ftype="fasta" />
-      <param name="col" value="1" />
       <output name="output1">
         <assert_contents>
           <has_line line="hg17" />