Improved separation of style and content/state/layout, and various other

[notEvil]

see https://github.com/victordiaz/PHONK/issues/139

• removed id, checked, enabled, hint, text, textOff, textOn, visibility, x, y, w, h from props
• removed documentation of style methods
• PViewMethodsInterface: added method id()
• PUI.getViewById: changed argument type from String to int
• PViewsArea: removed method addView(PViewMethodsInterface)
• added methods text(), textOn(String), textOn(), textOff(String), textOff(), checked()
• changed text(String) to return this
• changed textFont to preserve text style
• changed textStyle to preserve text font
• removed empty specializations of Styler
• removed unused instance variables