doc change: Add docs for SDK. Support new modular structure. In Android.mk, change @since level identifier to 5.xml, expose adt downloadable vars. Fix links that pointed to @sdkCurrent.

Change-Id:I368345755dd753b1056fb06ff25e4b32f3020e4d
Bug:2160782
diff --git a/docs/html/offline.jd b/docs/html/offline.jd
index 78e2679..fe70d50 100644
--- a/docs/html/offline.jd
+++ b/docs/html/offline.jd
@@ -10,17 +10,17 @@
 
 <h3>If you've downloaded the Android SDK for the first time...</h3>
 
-<p>Complete the online guide to 
-<a href="http://developer.android.com/sdk/{@sdkCurrent}/installing.html">Installing 
+<p>Follow the online guide to 
+<a href="{@docRoot}sdk/installing.html">Installing 
 the Android SDK</a>, which will help you setup your development environment
 (including the Android Development Tools plugin for Eclipse) 
 so you can start developing Android apps.</p>
 
 <p>Once your environment is setup, look at the
-<a href="http://developer.android.com/sdk/{@sdkCurrent}/installing.html#NextSteps">Next
-Steps</a> for some pointers that will teach you about Android and get you started.</p>
+<a href="{@docRoot}sdk/installing.html#NextSteps">Next
+Steps</a> for some suggestions on how to begin learning about Android.</p>
 
-<h3>If you've updated an existing SDK using the <em>SDK and AVD Manager</em>...</h3>
+<h3>If you've just installed new SDK components using the <em>SDK and AVD Manager</em>...</h3>
 
 <p>There's no additional setup.</p>
 
@@ -37,10 +37,11 @@
 Android developer documentation. The offline documentation offers almost all the same
 content and features as the online documentation. Because some features
 such as search and videos are network-based, not everything will work if you
-are not connected to the Internet.<br/><br/>
-For the most current documentation and fully-functional experience, please visit<br/>
-<strong><a href="http://developer.android.com">
-http://developer.android.com</a></strong>.
+are not connected to the Internet.</p>
+
+<p>For the most current documentation and a fully-functional experience, please visit:</p>
+<p style="margin-left:2em;">
+<a href="http://developer.android.com">http://developer.android.com</a></strong>.
 </p>