am ee58d1bf: 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.

Merge commit 'ee58d1bf9c54eaed623c4419e1d9db269a9c4137' into eclair

* commit 'ee58d1bf9c54eaed623c4419e1d9db269a9c4137':
  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.