Ubuntu: Fix not finding main.qml causing core dump

the qml files were still being copied to share/trojita and not share/

BUG: 333153
REVIEW:117419
Ubuntu: Enable viewing mailbox subdirectories

Mailbox view can now navigate through child mailboxes.

REVIEW: 117382
BUG: 332989

Fixed translation of Total & Unread message counts

Icon is copied from the ubuntu-mobile-icons package available from
http://packages.ubuntu.com/trusty/all/ubuntu-mobile-icons/download
and is available under the CC-BY-SA 3.0. Copyright by 2004-2012, Canonical Ltd.
Merge remote-tracking branch 'dpniel/mail_box'
Ubuntu messageListPage suppress error message caused by model being null

REVIEW: 117308
Ubuntu: support RoleMessageHasAttachments returning null QVariants

This fixes a nice QML warning "Unable to assign [undefined] to bool".