fixes #30

This may increase the db size by a factor of 1000 in the worst case and
it will need some fixes, when we decide to not show some events in the
timeline, but it should work for now.

Only consider the room as unread, if there is a message in the room and
only consider message and sticker events as messages.

fixes #65

This may still not raise the application correctly on some WMs, because
they don't allow disturbing the user with windows popping up. I don't
think we want to work around that.

fixes #84
fixes #113

fixes #97
fixes #51

remove setStyleSheet calls directly from widget code

removed from:
 - emoji panel scrollbars
 - emoji category labels
 - splitter image handles
 - textfield setTextColor impl

small change to the category separator label for better contrast /
readability in dark mode.

removed setTextColor completely from TextField. Doesn't appear to be in
use anywhere, and focus going more toward qss themeing from qproperty
setting.

Dark Theme qss cleanup

fixes #126

Tooltip and Combobox bugs with Breeze / Dark theme

setStyleSheet was overriding default tooltip theme from the system,
causing themes like Breeze to render white text on a grey bg for
tooltips. Tooltips now render default for the system theme everywhere.

set a theme matching color on the dark theme comboboxes.

fixes #118

Replace QHBoxLayout with QFormLayout in UserSettings

Use Nico's suggestion to just leverage the width of the field, and leave
a comment.

don't use members format camelCaseTail_

to save on recalculation of the size and having to subtract the margins
to do the tally, then re-apply.

Removed empty labels in favour of a fixed height and bottom alignment.

use QString instead of std::string (QStringLiteral doesn't have a
constructor with int, str.)

remove temp variable, and just deal with it inline.

Add Ubuntu 19.10 build requirements to README

 - Switch to {} widget initialization
 - set fixed size on the Toggles so they don't scale down vertically
 - add another setting section for INTERFACE
 - add a placeholder value for deviceFingerprintValue_ so it can calculate the right size.
 - fix warnings about `QLayout: Attempting to add QLayout "" to UserSettingsPage "",` in boxWrap
 - hide widgets properly in Q_OS_MAC
 - remove mainLayout_ completely
 - clean up resizeEvent

This allows form fields to wrap dynamically when they are too long for
the view. This should help mobile and small screen users to configure
the app without having to force it into portrait mode, or not be able to
reach the settings fields at all.