move run-tests.sh and pinentry-tests/ into assets, they are not external

external/ should be for submodules and the build system directly related
to the submodules.  pinentry-tests/ and run-tests.sh are installed into
assets/ but are not submodules nor part of their build system.  Therefore,
I moved them to assets/, and they no longer need to be installed.
add "Decrypt File" dialog to the debug suite
use bigger and hopefully non-corrupt test imagefile
use canonical path for lib/ in LD_LIBRARY_PATH

Otherwise, we have a ../ in the path, and who knows what part of the
Android guts might object to that...
make NativeHelper.gpg2 command send verbose output to stdout

This should make the verbose debug output show up in the DebugLogActivity
scrolling log view.
gpgme decryption does not currently work, handle Intents with gpg2 cmd line

This currently only handles incoming file URLs, like from ASTRO File
Manager.  It does not handle attachments from Gmail since those come in as
a stream/ContentProvider. That should probably wait until we get gpgme
decryption working.
add associations for known file extension to MIME types

I got these from the Free Desktop standards, i.e. looking at my own
machine in /usr/share/mime
switch things to use the standard file extensions

.asc and .gpg are overloaded and its very confusing, because the program
can't automatically know what kind of file it is.  If we use the PGP
extensions, we can help reduce some of that confusion:

skr = Secret KeyRing
pkr = Public KeyRing
working file encryption via SEND Intent: receives, encrypts, then SENDs

This code makes it so that gpgcli will receive arbitrary files via SEND
intents, then encrypts them to my hard-coded keyID, then launches a new
SEND Intent Chooser so the user can put the file somewhere useful.

TODO: the user needs to be able to choose who to encrypt to