Improve Android tracing instructions

Tracing of Java applications on Android is quite different from tracing native
executables, so move it to a separate file.

Add instructions on using wrapping support that appeared in Android 4.0, which
simplifies usage of apitrace on Android.

Add a reference to adjust-child-env tool that allows to inject tracing library
on Android without rebuilding and reflashing recovery image.

Signed-off-by: José Fonseca <jose.r.fonseca@gmail.com>
Rename Android.markdown to Dalvik.markdown.

As README still contains Android information.

Minor tweaks.