Fields not working then application runs as Runnable WAR

If application runs from runnable WAR (```java -jar app.war```) the plugin doesn't work,
test project https://github.com/yurib/TestGrailsFieldsPluginWar

Steps to reproduce:
1. Create application and one domain object in it
```
>grails create-app TestGrailsFieldsPluginWar
>cd TestGrailsFieldsPluginWar/
grails> create-domain-class Author
grails> create-domain-class Author
grails> create-scaffold-controller Author
```
Add *name* and *age* properties
Create custom field renders for the name:
```
ls grails-app/views/_fields/Author/name/
_displayWidget.gsp _displayWrapper.gsp _widget.gsp _wrapper.gsp
```
Run application:
```
grails>run-app
```
Observe custom field rendering.

Build and run Runnable WAR
```
grails>assemble
cd ./build/libs/
java -Dgrails.env=dev -jar TestGrailsFieldsPluginWar-0.1.war
```
Observe that field rendering as default without plugin override.

Use the linked TestGrailsFieldsPluginWar project to reproduce the difference between grails run-app and java -Dgrails.env=dev -jar ...war. Compare the custom renderers under grails-app/views/_fields/Author/name/, including _displayWidget.gsp, _displayWrapper.gsp, _widget.gsp, and _wrapper.gsp; done means the runnable WAR uses these overrides instead of the default field rendering.

Written by the indexing model from the issue text.