Changes

Use ImmutableList rather than AbstractList for CraftMetaBook
Although the AbstracList implementation does return a list, it is a of a
form that does not play well with libraries using reflection, such as
Gson. Leveraging a stream and the ImmutableList collector, this process
is greatly simplified (and cleaner).

Enable optional source JAR shading via profile shadeSourcesJar
mvn clean source:jar install -PshadeSouresJar
achieves this goal. If 'source:jar' is not specified the resulting 
source JAR will not include CraftBukkit sources. Not specifying
'install' will result in an unshaded CraftBukkit source JAR and not 
include other sources, making it useless for debugging purposes. Shade
CraftBukkit sources JAR.
Add maven-shade-plugin configuration directives to create sources JAR 
and shade contents thereof. This ensures when source:jar goal is run, 
relocated CraftBukkit source files are also relocated for debugging and
final code review purposes.