[IGN-572]Flex as default view type

[kgamble]

@PGriffith

Currently, the plan is to make the designer ‘remember’ your last selection, at the very least - so if you last made a flex container, as long as you keep your designer open, the selection will default to flex.

Woohoo! Its in a nightly now.

@sreis

572:New View Dialog: remember and default to the last created container type in Designer session
Perspective New View dialog now remembers the last created container type in the Designer session.

Long live the flex container!