[#3143] Review and update jopatai's work on the maven/ecj agent jar

* Update copyright headers
* Update code style (tabs, not spaces, spaces around + operator - that's about it)
* Use `x.class.getResourceAsStream`, not `x.getClass().` - minor mostly irrelevant nit.
* Rename and re-locate the jar itself.
* 'ecj' as an alias for this command seems a bit too cavalier' removed it.
* The source is in its own 'root' src dir, it doesn't really fit in the eclipse agent sources - it's more a maven agent.
* Fixed a bug where a filehandle wasn't safe closed. Mostly irrelevant (JVM would quite afterwards anyway).
* Slight rewording of the ecj docs.

buildScripts/create-eclipse-project.ant.xml

@@ -1,5 +1,5 @@
 <!--
- Copyright (C) 2010-2021 The Project Lombok Authors.
+ Copyright (C) 2010-2022 The Project Lombok Authors.
   
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
@@ -34,6 +34,7 @@ This buildfile is part of projectlombok.org. It creates the infrastructure neede
 			<srcdir dir="src/launch" />
 			<srcdir dir="src/utils" />
 			<srcdir dir="src/eclipseAgent" />
+			<srcdir dir="src/mavenEcjBootstrapAgent" />
 			<srcdir dir="src/installer" />
 			<srcdir dir="src/delombok" />
 			<srcdir dir="src/stubs" srcout="bin/stubs" />