Added selectable toolbar

[iiLubos]

  MMSelectableToolbar {
    id: selectableToolbar

    Component.onCompleted: index = 1

    model: ObjectModel {
      MMSelectableToolbarButton {
        width: Math.floor((pane.width - 40 * __dp) / 3)
        text: "Home"
        iconSource: __style.homeIcon
        checked: selectableToolbar.index === 0
        onClicked: selectableToolbar.index = 0
      }
      MMSelectableToolbarButton {
        width: Math.floor((pane.width - 40 * __dp) / 3)
        text: "Projects"
        iconSource: __style.projectsIcon
        checked: selectableToolbar.index === 1
        onClicked: selectableToolbar.index = 1
      }
      MMSelectableToolbarButton {
        width: Math.floor((pane.width - 40 * __dp) / 3)
        text: "Explore"
        iconSource: __style.globalIcon
        checked: selectableToolbar.index === 2
        onClicked:  selectableToolbar.index = 2
      }
    }
  }