Added option for Toggle button to show/hide the picker area.

I added an option to enable a Toggle button below the Palette area, to show or hide the picker area. This gives the user the option to have a limited number of colors to choose from, but also have the possibility to pick a different color, for advanced users.

I also updated the documentation and the example with the new options available.
This is for a specific reason. If you use the show/hide method and the palette is all the way to the right side of the screen and you click 'more', the picker will show up beneath the palette. To prevent this, I first move the palette to the left, to create some space for the picker to be rendered (with an extra margin of 5px). Then the 'applyOptions()' function takes care of the rest: shows the picker, and then moves the whole thing back to the right side of the screen.