SGF-465 - Moved project build to Maven.

Introduced Maven pom.xml basically mimicking what's been previously defined in build.gradle. Moved Asciidoctor files into places expected by the Spring Data build parent. Moved notice.txt etc. to src/main/resources. Switched to Logback for test logging.

src/test/resources/logback.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+
+    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d %5p %40.40c:%4L - %m%n</pattern>
+        </encoder>
+    </appender>
+
+    <logger name="org.springframework.data" level="error" />
+
+    <root level="warn">
+        <appender-ref ref="console" />
+    </root>
+
+</configuration>