add indicators instance and references to suite xml

For a case list (detail) field of this format `indicators:[<indicator set name>]/[<indicator name>]` add the following to the suite.xml:

```xml
<entry>
...
<instance id="indicators_{indicator set name}" src="jr://fixture/indicators:{indicator set name}"/>
...
</entry>
<detail id="...">
    <field>
        <header><text><locale id="..."/></text></header>
        <template><text><xpath function="instance('indicators_{indicator set name}')/indicators/case[@id = current()/@case_id]/{indicator_name}"/></text></template>
    </field>
</detail>
```