Add GWT compile reports and metrics flags

Add flags as checkboxes or options to the compiler.

For Maven Pom.xml interact with maven configuration. Implementation could be for multiple gwt maven plugins

Start by locating the compiler options and the Maven pom.xml integration points, then review how the supported GWT Maven plugins expose configuration. Done means the requested compile reports and metrics options are defined consistently and can be configured through the relevant Maven plugin integrations.

索引モデルが issue の本文から書いたものです。