Add command-line options for Gradle bootBuildImage parameters

This commit adds support for setting the image name and builder
parameters of the Gradle bootBuildImage task using command-line
options as an alternative to DSL configuration.

See gh-20520

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/bundling/BootBuildImageIntegrationTests-buildsImageWithCustomName.gradle

@@ -0,0 +1,11 @@
+plugins {
+	id 'java'
+	id 'org.springframework.boot' version '{version}'
+}
+
+sourceCompatibility = '1.8'
+targetCompatibility = '1.8'
+
+ bootBuildImage {
+	 imageName = "example.com/test-image-name"
+ }