This class is used to present modal dialogs and "wait screens" when the user should not access any other controls except those placed on the modal window
show()
shows modal window on top of all controls.
dismiss()
removes modal window from the screen.
addControl()
adds control to the modal window, can take value of standard NimbleKit controls, like NKActivityIndicator, NKButton, NKLabel, etc.
setAlpha(val)
sets the opacity of the modal window.
setFrame(x,y,w,h)
defines the frame size and positioning of the modal window.