BIGTOP-3103: Update download page to comply with Apache announcement requirements

To comply with announcement requirement, the download page should contain links
to all current and archived releases along with links to KEYS, checksums, and
signatures for all releases.
Current download page only provides link to latest one.

Signed-off-by: Jun He <jun.he@linaro.org>
diff --git a/src/site/xdoc/download.xml b/src/site/xdoc/download.xml
index 4ecaf8c..d431061 100644
--- a/src/site/xdoc/download.xml
+++ b/src/site/xdoc/download.xml
@@ -24,7 +24,7 @@
 	</properties>
 	<body>
 		<section name="Software downloads">
-			<subsection name="Releases" id="releases"></subsection>
+			<subsection name="Latest Release" id="releases"></subsection>
 			<p>
 				You can download the latest most stable release of Apache Bigtop project.
 				Source code of the framework will allow you to build, deploy, test, and
@@ -35,7 +35,7 @@
 			<ul>
 				<li>
 					The latest release of Apache Bigtop software framework <br/>
-					<a href="https://www.apache.org/dyn/closer.lua/bigtop/bigtop-1.3.0/">Bigtop 1.3.0</a>
+					<a href="https://www.apache.org/dyn/closer.lua/bigtop/bigtop-1.3.0/">Bigtop 1.3.0</a> (<a href="https://archive.apache.org/dist/bigtop/bigtop-1.3.0/bigtop-1.3.0-project.tar.gz.asc">pgp</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.3.0/bigtop-1.3.0-project.tar.gz.sha256">sha256</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.3.0/bigtop-1.3.0-project.tar.gz.sha512">sha512</a>)
 				</li>
 				<li>
 					Repositories of instsallable binary packages built with latest release
@@ -43,6 +43,25 @@
 					<a href="https://www.apache.org/dyn/closer.lua/bigtop/bigtop-1.3.0/repos/">Installable binary artifacts</a>
 				</li>
 			</ul>
+			<subsection name="Previous Releases" id="archived"></subsection>
+			<ul>
+				<li>
+					1.2.1 released on 2017-11-12<br/>
+					<a href="https://www.apache.org/dyn/closer.lua/bigtop/bigtop-1.2.1/">Bigtop 1.2.1</a>(<a href="https://archive.apache.org/dist/bigtop/bigtop-1.2.1/bigtop-1.2.1-project.tar.gz.asc">pgp</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.2.1/bigtop-1.2.1-project.tar.gz.md5">md5</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.2.1/bigtop-1.2.1-project.tar.gz.sha1">sha1</a>)
+				</li>
+				<li>
+					1.2.0 released on 2017-03-30<br/>
+					<a href="https://www.apache.org/dyn/closer.lua/bigtop/bigtop-1.2.0/">Bigtop 1.2.0</a>(<a href="https://archive.apache.org/dist/bigtop/bigtop-1.2.0/bigtop-1.2.0-project.tar.gz.asc">pgp</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.2.0/bigtop-1.2.0-project.tar.gz.asc.md5">md5</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.2.0/bigtop-1.2.0-project.tar.gz.asc.sha1">sha1</a>)
+				</li>
+				<li>
+					1.1.0 released on 2016-01-31<br/>
+					<a href="https://www.apache.org/dyn/closer.lua/bigtop/bigtop-1.1.0/">Bigtop 1.1.0</a>(<a href="https://archive.apache.org/dist/bigtop/bigtop-1.1.0/bigtop-1.1.0-project.tar.gz.asc">pgp</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.1.0/bigtop-1.1.0-project.tar.gz.md5">md5</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.1.0/bigtop-1.1.0-project.tar.gz.sha1">sha1</a>)
+				</li>
+				<li>
+					1.0.0 released on 2015-08-12<br/>
+					<a href="https://www.apache.org/dyn/closer.lua/bigtop/bigtop-1.0.0/">Bigtop 1.0.0</a>(<a href="https://archive.apache.org/dist/bigtop/bigtop-1.0.0/bigtop-1.0.0-project.tar.gz.asc">pgp</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.0.0/bigtop-1.0.0-project.tar.gz.md5">md5</a> <a href="https://archive.apache.org/dist/bigtop/bigtop-1.0.0/bigtop-1.0.0-project.tar.gz.sha1">sha1</a>)
+				</li>
+			</ul>
 		</section>
 	</body>
 </document>