Export keys and certificates in a zip file (kontalk-keys.zip)

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Dummy preference for importing personal key

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Fix personal key loading error after registration

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Import key pair process (preference not active yet)

This is a very basic and ugly import key pair process which uses the same
procedure of key regeneration, but instead it sends the imported key to the
server, which will accept it as valid.
Actual user interaction is still missing, it will be implemented soon.
After that, importing will be implemented also for the registration phase.

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Import key pair preference now working with warning dialog

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Show import completed correct message

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Prepare button for keys import during registration

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Import key from existing key pack archive during registration (UNTESTED)

The user will then continue to register normally, but Kontalk will use the
imported keys instead of letting the server signing it. The key is sent to
the server nonetheless because it needs to authenticate it.

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Importing keys from SD card working (WARNING using dummy passphrase)

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Ask for passphrase when importing keys during registration (UNTESTED)

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Warn user when something goes wrong during key import

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Hold/release message center on resume/pause

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Merge branch 'master' into desktopmods

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>

Conflicts:
	app/src/main/java/org/kontalk/authenticator/Authenticator.java
	app/src/main/java/org/kontalk/ui/PreferencesActivity.java
	app/src/main/res/values/strings.xml
	app/src/main/res/xml/preferences.xml