Move the default template imports to the build-link project

Other implementers of build link besides just SBT will want to use the same list of default template imports
Just to be on the safe side, to prevent people from doing silly things like dynamically modifying these lists, what about:

```java
private static final List<String> defaultTemplateImports;
public static final List<String> defaultJavaTemplateImports;

static {
  defaultTemplateImports = Collections.unmodifiableList(Arrays.asList(
      "models._",
      "controllers._",
      ...
  ));
  defaultJavaTemplateImports = Collections.unmodifiableList(
    new ArrayList<String>(defaultTemplateImports).addAll(Arrays.asList(
      "java.lang._",
      "java.util._",
      ...
    ))
  )
  ...
} 
```