Improve file more, Part 1

- Use Uris where it makes sense, Use File class to clarify it's a file (and not whatever else a string could be)
- Show sdcard in side menu in storage API #665
- Propose filename with gpg ending when storing it using the storage API #665
- Don't show output dialog on Android 4.4 #665
- Only show filename on Android < 4.4 #665

TODO:
- File deletion for Android < 4.4
- Testing (especially with Android < 4.4)
- Batch-encryption
- UI
- Temporary content provider (see #665 discussion)
Merge branch 'master' of github.com:mar-v-in/open-keychain into improve-file-more
Merge branch 'master' into improve-file-more
add create key capabilities to SaveKeyringParcel
Merge branch 'master' into improve-file-more

Conflicts:
	OpenKeychain/src/main/java/org/sufficientlysecure/keychain/KeychainApplication.java
	OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/DecryptFileFragment.java
	OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/EncryptFileFragment.java
	OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/FileDialogFragment.java
Missing import after merge
edit key: part 3
Add temporary file storage as discussed in #665

Writable from OpenKeychain, readable worldwide. Should be used to write shared files to it by first creating the file using TemporaryStorageProvider.createFile and then write to the Uri returned.
Encrypt/Decrypt UI work
don't use zero plural string for english

closes #703
forgot a line in previous commit
update spongycastle to include addSubkeyBindingCertification
fix subkey addition
use expert create key for key creation testing (revert this later on!)
Edit key: adding user ids
Add infographic from FSFE
Merge branch 'master' of github.com:open-keychain/open-keychain
edit key: work on saving
support changing primary user id in SaveKeyringParcel

Closes #695
Merge branch 'create-keyring'