drop another part of pornography in gi

more intuinitve configuration interface in graphicalitem. Improve code
for the future references (in case if new color type will be added).
Change X-AW-*Color values to ones with prefixes (added autoconversion
from old-version api)

sources/awesomewidgets/graphicalitemhelper.h

@@ -41,6 +41,7 @@ public:
     void paintVertical(const float &percent);
     // additional conversion methods
     float getPercents(const float &value, const float &min, const float &max);
+    bool isColor(const QString &input);
     QColor stringToColor(const QString &color);
 
 private: