Add a note that these indexes MUST NOT be changed

Thanks to paalsteek about hitting this in his work for the \Flagged column. I
should have coded this (see MainWindow::applySizesAndState) in an extensible
way.
Tasks: indicate activity via KeepMailboxOpenTask while it's fetching the UIDs and flags of new arrivals

This fixes that inconsistency while a GUI might fail to show any indication
while the network was stuck and we were waiting for the UIDs to arrive.

REVIEW: 116989
handle columns added to the MsgListModel and adjust their width
Icon for flagged mails added

mail-flagged is Oxygen's actions/flag-red.png
mail-unflagged is derived from Oxygen's actions/flag-red.png
Adds autopilot testsuite setup for Ubuntu Touch client

REVIEW: 116954
Highlight flagged messages in the MessageListView

REVIEW: 116942
Prevent assert failure when called with option -a without an value
Merge remote-tracking branch 'paalsteek/master'
Qt5: reimplement QAbstractProxyModel::sibling so that it isn't broken

The Qt5 changed the way how QAIM::sibling works. Instead of being hardcoded
within the QAIM, it is now a virtual which can be (and is) overriden by the
derived classes including the QAbstractProxyModel.

It turns out that the QAbstractProxyModel's implementation by default doesn't
support proxies which happen to reorder the items within the model. As of the
5.2 branch, Qt's implementation of QAbstractProxyModel::sibling simply
translates the parent of the index in question and uses the row/column as
offsets within the *source model*. This is arguably a bug; the Qt4 code instead
looked at the parent within the proxy itself, and used row/column as offsets
within the proxy, which is also what the user code asked for.

Qt5 upstream fix (under review right now) at
https://codereview.qt-project.org/81685 .

REVIEW: 117027
Add a custom role for showing a quick attachment indicator

Thanks to luthrak and paalsteek for review.

REVIEW: 117033
Column for the attachment indicator added to the MsgListView
GUI: show the attachment indicator by default
GUI: move the attachment indication to the left
add .reviewboardrc

REVIEW: 117046
Merge branch 'master' of git://gitorious.org/trojita/hades-trojita
Merge branch 'attachment-indication'

REVIEW: 117048
Fix missing inline copyright header for QMF stuff

It seems that back in 2009 when moving pieces of code between separate files I
forgot to add a proper copyright notice to the target files. Some stuff
(low-level encoding of RFC2047/quoted-printable/... bits) was imported from the
Qt Messaging Framework without copying an appropriate notice to the file header.
This is a mistake, and I hereby apologize for that. The top-level LICENSE file
already lists this contribution.

Thanks to Valério Valério (VDVsx on IRC) for bringing this to my attention.
Created a popover sheet for Ssl info and acceptance

REVIEW: 117084
Change UI for MessageListPage.qml in Ubuntu port

REVIEW: 117028
Ubuntu: fixes for the launcher

- Switch to QCommandLineParser for argument parsing
- Fix problems with using relative paths and add option for autopilots'
  `-testability` command line arg to enable autopilot interface

REVIEW: 117030