TextBundle#get method to check for the key. If the key does not exist,
return a string indicating was is missing to help track this down in the
future.
1. This change introduces the current SWT builds that exist in Maven;
removing the need to locate and capture the JAR files.
2. The current SWT change is to capture the new Mac OS X aarch64 builds
("Apple Silicon").
3. The current version of SWT, however, requires Java 11.
4. Due to the complexity of the prior Gradle build, it was restructured.
