Add test tool for default ext handling in discovered collections

<tool id="discover_default_ext" name="discover_default_ext" version="0.1.0">

    <command><![CDATA[

echo 1 > 1.txt;

]]></command>

    <inputs />

    <outputs>

        <collection name="collection_with_default_ext" type="list" label="with default format" format="fasta">

            <discover_datasets pattern="__name_and_ext__" />

        </collection>

        <collection name="collection_default_ext_and_explicit_format" type="list" label="with default format and static element format" format="fasta">

            <discover_datasets pattern="__name__" format="txt" />

        </collection>

        <collection name="collection_default_ext_used" type="list" label="with default format and no override" format="fasta">

            <discover_datasets pattern="__name__" />

        </collection>

        <collection name="collection_without_default_ext" type="list" label="wihtout default ext, should be data">

            <discover_datasets pattern="__name__" />

        </collection>

    </outputs>

    <tests>

        <test expect_num_outputs="4">

            <output_collection name="collection_with_default_ext" type="list" count="1">

                <element name="1" ftype="txt">

                    <assert_contents>

                        <has_text text="1" />

                    </assert_contents>

                </element>

            </output_collection>

            <output_collection name="collection_default_ext_and_explicit_format" type="list" count="1">

                <element name="1.txt" ftype="txt">

                    <assert_contents>

                        <has_text text="1" />

                    </assert_contents>

                </element>

            </output_collection>

            <output_collection name="collection_default_ext_used" type="list" count="1">

                <element name="1.txt" ftype="fasta">

                    <assert_contents>

                        <has_text text="1" />

                    </assert_contents>

                </element>

            </output_collection>

            <output_collection name="collection_without_default_ext" type="list" count="1">

                <element name="1.txt" ftype="data">

                    <assert_contents>

                        <has_text text="1" />

                    </assert_contents>

                </element>

            </output_collection>

        </test>

    </tests>

</tool>

  <tool file="collection_cat_group_tag.xml" />

  <tool file="collection_cat_group_tag_multiple.xml" />

  <tool file="discover_sort_by.xml" />

  <tool file="discover_default_ext.xml" />

  <tool file="expression_forty_two.xml" />

  <tool file="expression_pick_larger_file.xml" />

  <tool file="expression_parse_int.xml" />