allow for configurable output location, bump version

@alonle @liorhar needed to allow the proto plugin to generate the classes in a committable location 
Code is same as here : 
https://github.com/aantono/gradle-plugin-protobuf/blob/13dca09338752d7019d615091e5615aad9a0fd70/src/main/groovy/ws/antonov/gradle/plugins/protobuf/ProtobufPlugin.groovy#L94

to comply with plugin standard