in GnuPG.gpg2(), run gpg2 in a shell and output stdout/stderr to logcat

Using NativeHelper.gpg2 in a CommandThread seems to trigger pinentry fine,
so I figured perhaps its related to running the command in /system/bin/sh.
This also dumps stdout/stderr to logcat so we're not flying blind.

refs #1560
rename MESSAGE_OKAY to MESSAGE_OK

This mirrors the Android style, e.g. RESULT_OK, etc.
split out EncryptFileActivity's process into separate methods

This makes the process a lot clearer, and makes it easier to share the
Handler and Messenger once the Fragment/AsyncTask for running GnuPG.gpg2()
is in place.
run gpg2 operations in a custom AsyncTask+Dialog fragment

GnuPG.gpg2() always needs to be run in a thread, otherwise it'll block
PinEntryActivity from starting up, if its needed.

fixes #1560
add option to sign when encrypting using EncryptFileTo

refs #1438
ImportFileActivity: split out actions from Handler into methods

Just to make things clearer, especially as this class is ported to use
the Gpg2TaskFragment.
convert ImportFileActivity to use Gpg2TaskFragment and its AsyncTask

GnuPG commands need to be run in an AsyncTask, otherwise they block
the PinEntryActivity from being launched.

closes #1560
CreateKeyActivity: fix bad path for exported secret key backup

refs #1460
CreateKeyActivity: do not upload to keyserver by default

Since it is hard to undo the upload, this should not be on by default.
CreateKeyActivity: create properly formatted params to fix gpgme key gen

The parameters in the "params" string need to be in a specific order,
otherwise the ken gen process fails. gpgme does not give very specific
error messages, but since the data format is almost the same as
`gpg2 --gen-key myparamsfile`, its easy to test the params file there.

refs #1460
CreateKeyActivity: put entire gen-key process in try/catch block for clarity

This also makes it easy to do things like getCanonicalPath() without
having to add another try/catch block.

refs #1460
CreateKeyActivity: add ProgressDialog with status messages

A simple set of messages to show what stage the process is on.  This should
be expanded to get the progress output from gpg2 to give the user more
feedback, since the key gen process can take so long.

refs #1460
add "Settings" to the main menubar, with priority over "Debug Mode"
add "Send Key" debug method for uploading to the key server

This also moves the title strings to strings.xml and adds window messages
to the prompt dialog.
CreateKeyActivity: show gen-revoke as disabled since it doesn't work yet

refs #1372 refs #1481
CreateKeyActivity: return result, send broadcast, & finish upon completion

This adds a method that sends the setResult() for the calling Activity,
sends a broadcast to refresh the key view, and calls finish() to make
CreateKeyActivity disappear.  It also shows a Toast if it failed.

closes #1550
use correct string for Decrypt File dialog
DebugLogActivity: ActionBar-ify the menu

reorder, add icons, and allow items to show up as actions
handle incoming .skr and .pkr files by launching prompt to import them

refs #1454 refs #1455