Feature: Create Service for Dialog

[jigargandhi]

Dialog component on its own is of little use. Angular material provides $mdDialog service that helps in creating dialogs with various configuration.

An angular service $uifDialog needs to be created that provides functionality to create dialogs on the fly.
/cc: @andrewconnell @ngOfficeUIFabric/ngofficeuifabric-members

[jigargandhi]

Methods

$uifDialog.alert()

$uifDialog.confirm()

$uifDialog.prompt()

$uifDialog.show()

$uifDialog.hide()

$uifDialog.cancel()

The parameters of these functions can be similar to $mdDialog

@andrewconnell: Let me know if more detailing is required /cc: @ngOfficeUIFabric/ngofficeuifabric-collaborators

[andrewconnell]

IDK... I think I'd personally like to see more usage of what this would look like from a controller to be sold on this service. Then again, it's an enhancement & I get why MD has it... so if you want to tackle it, I say go for it @jigargandhi

[andrewconnell]

But... need to see more of a spec before you go building so we can all agree :)

[andrewconnell]

Closing... see #455