Minimum required changes to support convention-based View resolution.

The meat is on lines 98 and 99.  If we use the _url_ property of the built SoyView, we can utilize the _prefix_ property of _ViewResolver_.  As in:

```xml    
<bean id="soyViewResolver" class="pl.matisoft.soy.SoyTemplateViewResolver">
    <property name="prefix" value="app."/>
    <property name="debugOn" value="${app.debug}"/>
    <property name="templateFilesResolver" ref="soyTemplateFilesResolver"/>
    <property name="templateRenderer" ref="tofuRenderer"/>
    <property name="tofuCompiler" ref="tofuCompiler"/>
    <property name="globalModelResolver" ref="soyRunTimeGlobalModelResolver"/>
    <property name="localeProvider" ref="soyLocaleProvider"/>
    <property name="soyMsgBundleResolver" ref="soyMessageBundleResolver"/>
    <property name="encoding" value="UTF-8"/>
    <property name="order" value="0"/>
</bean>
```

A default viewName is provided to handle the case where a View is dispatched to /.