Validate chat ID before joining

Only add a new chat conversation after we ensured that the chat ID
exists.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Display an error message when trying to join a chat

Pidgin currently crashes if the user tries to join a chat by using the
"Join a Chat..." feature of Pidgin. Since WhatsApp does not allow for
joining a chat by name at all, display an error message instead.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Split out chat participant retrieval

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Add .mailmap

Conflate all of David's mail addresses.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Merge pull request #44 from cryptocrack/fix-default-resource

Fix default resource
Merge pull request #45 from cryptocrack/add-mailmap

Add .mailmap
Merge pull request #42 from cryptocrack/chat-join-fixes

Chat join fixes
Factor out incoming message processing

Split out common code that is used for adding an incoming chat message
to a conversion.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Fix author retrieval for group chat images/sounds

Get the actual author instead of using uninitialized data for the author
name if an image, sound or location is sent to a group.

Signed-off-by: Lukas Fleischer <info@cryptocrack.de>
Merge pull request #46 from cryptocrack/group-receive-image-fixes

Group receive image fixes