Upgrade to official build tools 1.0 and add gradle wrapper.

The wrapper is for people who might be on Windows or not used to a gradle build system. They can just run commands with ./gradlew instead of having to install gradle themselves.

Sorry for so many PR's so quickly! Not sure if you wanted them in bigger pieces or smaller ones :\
So, library projects are allowed to have Manifest files that describe project attributes (min/target SDK, supported devices, etc). The manifest merger takes care of figuring out the merging between manifests. 

This process/tool is described here: http://tools.android.com/tech-docs/new-build-system/user-guide/manifest-merger#TOC-Manifest-files-ordering