docs: Rewrite of App Fundamentals.. Part 3
This introduces two new docs:
Application Fundamentals:
This is the homepage for the app fundamentals; it introduces
the security sandbox, each of the component types, intents,
the manifest file, and app resources.
Processes and Threads:
Most of this document is from the original fundamentals.jd doc;
it describes more about how an app's process runs on android
and the different levels of process importance used to determine
which processes the system can kill and how threads are and
should be used in an application. I've added more detailed information
about threads, however, including information about using AsyncTask.
These documents are orphaned for now. This is the last set of documents
required before I'll change the side navigation to adopt the new
app fundamentals and redirect the old fundamentals.jd file.
Change-Id: Ica5f7f683df76b488552939ee0888e796204f2c1
b65b2df6e4