gradle plugin project scaffolding.
Copy and wire up maven plugin in gradle.
Add weaving support to artemis gradle plugin.

- adds 'weave' target.
- usage example in 1.3.1 libgdx project:

```groovy
buildscript {
    dependencies {
        classpath 'net.onedaybeard.artemis:artemis-gradle-plugin:0.7.1-SNAPSHOT'
    }
}
```

desktop/build.gradle

```groovy
apply plugin: "artemis"

weave {
    enableArtemisPlugin = true
    enablePooledWeaving = true
    ideFriendlyPacking = true
    optimizeEntitySystems = true
    classesDir = project(':core').sourceSets.main.output.classesDir
}

weave.dependsOn build
dist.dependsOn weave
```
Mavenize gradle plugin build process.
ALL HAIL THE TAB LORD.
.. and the linebreak princess.
Update javadoc for PackedWeaver and PooledWeaver.
Merge pull request #176 from junkdog/feature-gradle-plugin

Gradle weaving plugin