Investigate Gradles development

[chkpnt]

The plugin was initially developed when Gradle 2 was current.

[chkpnt]

Generating a plugin-classpath.txt is not needed anymore (57ea81d).

[chkpnt]

With f174115, I could get rid of java.lang.Integer.

[chkpnt]

Seem that with gradle/gradle#813, Gradle supports java.nio.file.Path, so this mapper is probably not needed anymore.

truststorebuilder-gradle-plugin/src/main/kotlin/de/chkpnt/gradle/plugin/truststorebuilder/ImportCertsTask.kt

Lines 38 to 44 in 1f10a66

	interface FileAdapter {
	fun toFile(path: Path): File
	}
	class DefaultFileAdapter : FileAdapter {
	override fun toFile(path: Path): File = path.toFile()
	}