Removes as many Gradle 7.0 compatibility issues as possible
* `baseName` -> `archiveBaseName`
* `extension` -> `archiveExtension`
* `destinationDir` -> `destinationDirectory`
* `runtime` -> `runtimeOnly`
* Change some log4j-api and log4j-core dependencies
* Remove an unneeded and outdated plugin (`net.ltgt.apt`)
* tweak the plugin-api change detector's property annotations.

Warnings still exist with one external plugin used for license file
checking that we do not control the source code for.

Signed-off-by: Danno Ferrin <danno.ferrin@gmail.com>