guice-persist - bound Properties improovement

_From [raimondas.valickas](https://code.google.com/u/raimondas.valickas/) on March 27, 2012 11:22:35_

Add support for named properties in JpaPesistModule, as JpaPersistModule#properties() method requires Properties class instance. In most cases, Properties instance is already bound to some kind of annotation or name, however, it cannot be accessed until injector is fully created.

for example new JpaPersistModule("jpa").properties(Names.named("configuration"))

(... or allow the developers to bound properties by themselves by un-protecting Jpa annotation, as it was in warp-persist).

_Original issue: http://code.google.com/p/google-guice/issues/detail?id=695_