new mobile components

Summary:
ApplicationWindow: extension of QQC ApplicationWindow, as other mobile components is based upon pageStacks, but this uses the PlasmaExtras PageRow instead as suggested in the higs (will have to be seen if pageRow will have to be copied here as well for dependency issues)

ActionGroup: extension of QQC Action, it can have children, needed for hyerarchical menus in the GlobalDrawer

GlobalDrawer: default drawer for the left, contains a title with an icon (usually app icon and title), and a menu of actions that can be a tree: opening a subcategory works "kickoff style" with the menu sliding in the subcategory and the possibility to go back by swipe)
below the menu, arbitrary custom items can be embedded

ContextDrawer: default context drawer with a title and a list of actions, nesting not allowed

Page: similar api to other component sets (plasma components has one too, will depend if we can depend from them wether have a copy here in the end i guess) it has an actions property that will create a row of round buttons at the bottom of the page, if the main item f the page is a scrollView or a Flickable, use the scrolling to hide/show the buttons.
This element is supposed to be stuffed into the ApplicationWindow internal PageRow in order to make possible back navigation with swipe

Reviewers: davidedmundson, Plasma:_mobile

Reviewed By: davidedmundson, Plasma:_mobile

Subscribers: davidedmundson, plasma-devel

Differential Revision: https://phabricator.kde.org/D409