Allow property for release type

[cdschneider]

release.useAutomaticVersion is nice for Jenkins/CI builds where the tagged version will be the version minus the -SNAPSHOT but when people want to cut major, minor, bug-fix releases (among other release types based on other versioning strategies), they need to specify the release.releaseVersion property to whatever version they want every time they cut a release.

It'd be nice if we could automate the setting of the releaseVersion property based on the release "type" that a user wants.

So along with using the release.useAutomaticVersion flag, we could make an optional second and/or complementary flag that looks something like:

$ ./gradlew release -Prelease.useAutomaticVersion=true -Prelease.releaseType=<bug|minor|major>

This would:

1. Skip the prompt for confirming the release version
2. Change version to the correct next non-SNAPSHOT version for tag/release. ie if development version is 1.0.1-SNAPSHOT and I want to cut a major release, the tag would actually get bumped prior to release to 2.0.0. If I wanted a minor release, the tag would get bumped to 1.1.0.

[mageddo]

This is a great feature