PrivateFilesProvider: add debugging logging for the unsupported methods

This allows us to see what the apps that use this ContentProvider are
asking for.
REBASE Revert "FileHandlerActivity: remove VIEW with */* mimetype, use SEND for generic files"

This reverts commit 349507acc5ed79132889b5eca5c4738f7647d228.
REBASE Revert "SEND_MULTIPLE is not implemented yet so do not receive it"

This reverts commit 9a2db294b67dbae795268adcdf0d807eecbd2e54.
REBASE add ContentProvider to read from private files, to sent via VIEW Intents
accept *.bin files, some email clients name PGP attachments that way

refs #1455 refs #1456
REBASE Revert "all IntentFilters should have category.DEFAULT, and safe ones .BROWSABLE"

This reverts commit b9f032406f9e725fce829f76ea12e55bc69196f5.
REBASE accept *.bin files, some email clients name PGP attachments that way
EncryptFileActivity: "Encrypt file to" in Contacts does not include URI

When starting a file encryption from the Contacts app, it will not provide
a URI to the data, the user will be prompted for that later.
FileHandlerActivity: harden to make it accept all sorts of Intents

The data can arrive in a wide variety of forms, so there needs to be a lot
of checking for nulls, and trying to find stuff in multiple places.

refs #1454 refs #1455 refs #1456
REBASE claim openpgp4fpr: URI scheme and launch dialog to receive from keyservers
every Activity should have a label, i.e. 'android:label'