Add vector logo.
Qualify the plugin ID.
Bump version of plugin to 1.2-SNAPSHOT.
Support custom exclusions when packaging templates.

Implements issue #95. The Lazybones extension now supports a `packageExludes`
property and a corresponding `packageExclude()` method that allows users of
the Gradle plugin to specify extra Ant patterns to prevent things like editor
and IDE files from being included in the packaged templates.
Allow numbers in project template names (Gradle plugin).

Fixes issue #123. The `package...` tasks weren't working for project templates
that had numbers in their names. This change allows people to use things like
Neo4j and EasyAs123, which get converted to neo4j and easy-as123 respectively.

If the name conversion doesn't work for you, there is also the option to run
the package task in hyphenated for, e.g.

    gradle packageTemplate-easy-as-123

This works as long as the first character after `packageTemplate` is a hyphen.
Explain in comment why convention mapping is not used.
Defer validation of template directories.

Fixes issue #126. The Gradle plugin needs to check that the required template
directory exists and that it has a VERSION file before attempting to package
it. This used to happen during the configuration phase, but this prevents
builds from generating the template directory or VERSION file at execution
time.

The actual validation is now done immediately before the packaging takes place.
The build doesn't fail quite so fast now, but it does fail at a better time.