Remaining things after refining

[tomneda]

There are still some things left on the master which come from the refactoring (can happen when changing hundred of lines) and other very tiny changes:

• The zoom factor did not change the x-axis values.
• A not allowed zoom factor (4 at half side view) led to a "division by zero" (ls-scope.cpp:169).
• Small correction in README.md and radio.ui.
• Add excludes to .gitignore for VSCode and JetBrains IDE users (like me :-), beside QTCreator ).
• I move the compiler switch DO_STEREO_SEPARATION_TEST (not activated) to fmreceiver.pro (CMakeFiles.txt may follow if needed).
• An initialization issue which meanwhile are longer in the code (since 3276877#diff-017ed302f9eb902069c2e9247a3eab6f556f78c0cd9a2eaeda0f6c2be123ee3aL1009 ): the member "currAttSliderValue" was not more initialized. This doesn't matter unless the IQ balance slider was not touched. In the current AppImage the compiler switch DO_STEREO_SEPARATION_TEST is activated (was that deliberately?) so the IQ balance slider did not use the not initialized member and no problem happens.

The fixes above would not change important things (or show no effects) in the current AppImage or Windows setup. So they need not to be rebuild (imo). But it would be good (gives me a better feeling :-) ) if they are on the mainline.