Add gradle build files

- First set of changes for introduction of a gradle build.
- Relates #470

spring-shell-management/spring-shell-management.gradle

@@ -0,0 +1,18 @@
+plugins {
+	id 'java-platform'
+	id 'maven-publish'
+}
+
+javaPlatform {
+	allowDependencies()
+}
+
+description = 'Spring Shell BOM'
+
+dependencies {
+	api platform("org.springframework.boot:spring-boot-dependencies:$springBootVersion")
+	api "org.jline:jline:$jlineVersion"
+	api "org.jline:jline-terminal-jna:$jlineVersion"
+	api "org.antlr:ST4:$st4Version"
+	api "com.google.jimfs:jimfs:$jimfsVersion"
+}