Context menu

Context menu is implemented by mtd-context-menu, mtd-dropdown custom directives.

mtd-context-menu has position logic and that is proxy for mtd-dropdown and triggered by contextmenu event.

mtd-dropdown is wrapper of several directives that has following structure.

<md-whiteframe>
  <md-button ng-repeat>
    <md-icon></md-icon>
  </md-button>
</md-whiteframe>