Modernizing the documentation

I made this project match the other Spring projects for documentation by pulling in spring-doc-resources and using those resources to create the dynamic ToC and our new styles.

Accounting for Glenn Renfro's feedback

Glenn caught a couple problems. I have fixed them. Thanks, Glenn. :)

spring-cloud-task-docs/src/main/asciidoc/index-docinfo.xml

@@ -1,14 +0,0 @@
-<productname>Spring Cloud Task</productname>
-<releaseinfo>{spring-boot-version}</releaseinfo>
-<copyright>
-<year>2016-2019</year>
-<holder>Pivotal Software, Inc.</holder>
-</copyright>
-<legalnotice>
-<para>
-	Copies of this document may be made for your own use and for distribution to
-	others, provided that you do not charge any fee for such copies and further
-	provided that each copy contains this Copyright Notice, whether distributed in
-	print or electronically.
-</para>
-</legalnotice>

spring-cloud-task-docs/src/main/asciidoc/index.adoc

@@ -39,11 +39,23 @@ Michael Minella, Glenn Renfro, Jay Bryant
 :attributes: allow-uri-read
 // ======================================================================================
 
+(C) 2009-2018 Pivotal Software, Inc. All rights reserved.
+
+Copies of this document may be made for your own use and for distribution to
+others, provided that you do not charge any fee for such copies and further
+provided that each copy contains this Copyright Notice, whether distributed in
+print or electronically.
+
 include::preface.adoc[]
+
 include::getting-started.adoc[]
+
 include::features.adoc[]
+
 include::batch.adoc[]
+
 include::stream.adoc[]
+
 include::appendix.adoc[]
 
 // ======================================================================================