Convert to multi-module project

Rename current module to mailbox-android and add modules for common code as well as the command line interface

changed milestone to %Mailbox

added Sponsor 6 label

marked this issue as related to #1 (closed)

part of #1 (closed)

mentioned in merge request !5 (merged)

mentioned in commit 9ff39b88

closed with merge request !5 (merged)

added Mailbox label

added Weight: 1 label

added R: fixed label

added Mailbox app label