Fixes "sent an audio file" replies, that were actually replies to text
messages.

I'm not sure, if that is the right way, but Qt doesn't really have a way
to format custom localised dates, so I tried to find the closest
approximations to what we currently have.

Relates to #69

Currently translated at 37.4% (65 of 174 strings)

Translation: Nheko/nheko
Translate-URL: http://weblate.nheko.im/projects/nheko/nheko-master/de/

Currently translated at 34.5% (60 of 174 strings)

Translation: Nheko/nheko
Translate-URL: http://weblate.nheko.im/projects/nheko/nheko-master/de/

Currently translated at 31.6% (55 of 174 strings)

Translation: Nheko/nheko
Translate-URL: http://weblate.nheko.im/projects/nheko/nheko-master/en/

Currently translated at 5.2% (9 of 174 strings)

Translation: Nheko/nheko
Translate-URL: http://weblate.nheko.im/projects/nheko/nheko-master/en/

Currently translated at 5.2% (9 of 174 strings)

Translation: Nheko/nheko
Translate-URL: http://weblate.nheko.im/projects/nheko/nheko-master/en/

Currently translated at 48.9% (85 of 174 strings)

Translation: Nheko/nheko
Translate-URL: http://weblate.nheko.im/projects/nheko/nheko-master/de/

Currently translated at 3.4% (6 of 174 strings)

Translation: Nheko/nheko
Translate-URL: http://weblate.nheko.im/projects/nheko/nheko-master/en/

Respect system styling
Increase size of emojis (to remove empty space)
Add hover effect (partially adresses #41)
Less hardcoding of sizes
Use emoji font (color)

Mentions are now an '@' icon in the upper right.

UI Popup is now a smaller dialog.

Still lots of work to be done here.

If the QMimeData contains an image, it actually has a mime type of
application/x-qt-image. At least in some cases accessing the image/*
data returns a 0 length array. Accessing the data via ->imageData works
however. So we use that as our accessor and pass it to the preview
dialog.

fixes "Attribute Qt::AA_EnableHighDpiScaling must be set before
QCoreApplication is created."

Add a RoomListItem-like button that opens a dialog
containing all of the messages that would result in a
highlight from the server (for example, the user is mentioned,
or @room is mentioned).

This is VERY rudimentary and will be completely reworked in the future
to take advantage of the existing TimelineView class, instead of
using a dialog like it does now. The button to show the mentions
also needs work.

Update to mtxclient 0.3.0

Add .well-known support

fixes #9 

fixes #9

Removed RPATH from compiled binaries

Signed-off-by: Vitaly Zaitsev <vitaly@easycoding.org>