Support @Grab without a version or group

Usually, use of @Grab requires you to specify a group, module, and
version when identifying a dependency. This can be done in two
different ways:

@Grab(group='alpha', module='bravo', version='1.0.0')
@Grab('alpha:bravo:1.0.0')

This commit allows users to only specify a module: the group is
inferred and the version is the one dictated by the boot CLI. Both
forms are supported:

@Grab(module='bravo')
@Grab('bravo')

Groovy's global AST transformations, which is how Grab is implemented,
do not support ordering and we need to augment the AST for the Grab
annotation before its processed by the Grab AST transformation. To
work around this, reflection is used to get hold of the compile
operations in the conversion phase, and a new AST transformation is
inserted immediately before the first AST transformation operation.

To allow a module's groupId and version to be resolved consistently,
META-INF/springcli.properties has been enhanced to include properties
for each module that we want to support in the following form:

<module>.groudId = <groudId>
<module>.version = <version>

<groupId> and <version> are taken from the Maven project's
dependencies.

VPP, a Velocity-based pre-processor is used to automatically generate
the enhanced properties file.