Basic UI components

- Add first preliminary model of building and working with
  higher level components.
- Components for text input, path input, single selector and
  multi selector.
- Components renderings are based on ANTLR ST templates while
  there is support for building rendering output manually.
- Add these into sample.
- This is a base of additional work what goes to these components
  and concepts around it.
- Relates #360

spring-shell-core/pom.xml

@@ -52,6 +52,15 @@
 			<artifactId>assertj-core</artifactId>
 			<scope>test</scope>
 		</dependency>
-
+		<dependency>
+			<groupId>org.awaitility</groupId>
+			<artifactId>awaitility</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>com.google.jimfs</groupId>
+			<artifactId>jimfs</artifactId>
+			<scope>test</scope>
+		</dependency>
 	</dependencies>
 </project>