3djc/horus improve mixer setup (#3636)

* Rework to display bar on mixers, hence needs a more flexible drawSingleXXBar approach

* First working version
WARNING : displayMixConvertMask() DOES have a bug, do NOT PR without fix

* Fixed displayMixConvertMask() bug
Cosmetics on placement on status bar

* Cosmetics

* Improved graphics by mhotar !

* Fix for multiple lines mixers
Cosmetics

* Fine tune column values to handle more complex mixers lines

* Replace +=, *=, := by icons

* No needs to use mask bitmap

* Remove unwanted png file

* Fix handling and conversion of Mask to Bitmap

* use loadAndConvertMask here too

* Typo

* Screen layout fine tune

* - Move loadMaskOnBackground to framebuffer.cpp
- replace loadMaskAndConvert by loadMaskOnBackground

* Cosmetics

* Move new icons to theme loading

* Fine tune Mixer setup screen on darkblue

radio/src/gui/horus/bitmapbuffer.h

@@ -177,6 +177,8 @@ class BitmapBuffer: public BitmapBufferBase<uint16_t>
     static BitmapBuffer * load(const char * filename);
 
     static BitmapBuffer * loadMask(const char * filename);
+    
+    static BitmapBuffer * loadMaskOnBackground(const char * filename, LcdFlags foreground, LcdFlags background);
 
     void drawMask(coord_t x, coord_t y, BitmapBuffer * mask, LcdFlags flags, coord_t offset=0, coord_t width=0);