Apply custom background only to top level controls widget

This matches the behavior of the windows launcher and makes things
easier to see on some Qt styles
Use correct image for run button
Handle errors when starting game process
Merge remote-tracking branch 'origin/background-fix'
deleting non-existant mods from saved settings
Corrected spelling, grammar, links, and general layout of README.md
Corrected visibility while selecting within mainwindow

Removed selection-background-color in stylesheet of listDLC and listMOD, and modified palette in order to aid in visibility of table values while selecting.
changed start command in mainwindow.cpp to startDetached to prevent game closing after launcher
add bin folder that stores launcher binary
Release 3
Fix mods lookup, eliminate some copy&paste.
Merge commit '3a29302ef49e533f291dcb33f6da577dce3ec56f' of github.com:alfonsojon/Qt-EU4-Launcher