Simplify symbol loading in QML.

* This adds a File object to QML which allows to test if a file exists.
* This simplifies to QML code a lot.
* This allows moves all symbols into the Qt resource file, which avoids
  path problems when loading the symbol or testing for its existence.

This allows to add new symbols without changing the code.
Just add them to the resource file with the correct key name and it
will be picked up automatically.
Remove png files from install target.
Add Qt::Tool window flag to avoid displaying a taskbar entry

for the qmlapplication window.
Also removed displaying qmlwindow and config dialog after startup.
Remove obsolete path from pic.
Add settings object to allow QML configuration.
add empty README.md
update README.md
Add licensing info: GPLv3
Add -Wall compiler switch and fix warnings.
Fix debug string.
Make config dialog working.
Add developer option to override device file to use.

This is only enabled when the TEST macro is defined for security reasons.
Add analyse.sh to run ccc-analyzer.