Add drag-and-drop of customizer controls and have that update order in preview

[westonruter]

The widget form controls in each sidebar customizer section could re-ordered via drag-and-drop.

[bobbravo2]

Added in pull request #14

[westonruter]

@bobbravo2 thanks!! I did a code review of your pull request. Sorry for the barrage of comments, but I hope they're helpful! Once you process my feedback, I'll pull your commits into this issue directly (creating a issue-1-drag-n-drop branch), and we can then continue collaborating by my pushing my and your commits to this branch, and you can pull down commits from the branch to continue working in your fork.

[bobbravo2]

@westonruter just caught your comments here. NP with the comments - I really appreciate the feedback! I'm pretty sure I've addressed everything... let me know :-D

[westonruter]

@bobbravo2 as I commented on your PR #14, I merged in your commits into the issue-1-reordering branch, which I then converted into an internal pull request from that branch to the develop branch. I'll continue merging in additional commits you have from your develop branch.

[bobbravo2]

I thought you were on Vacation! I caught you on IRC at some point. Have a great Vaca, We'll catch up next week

[westonruter]

@bobbravo2 note the addition of items which prevents the section description from being draggable, and the addition of the axis since it only makes sense to drag vertically.

[westonruter]

@bobbravo2 @shaunandrews OK, I've added commits to make widget re-ordering previewable, and to lay the groundwork for adding and deleting widgets via customizer. Please check it out (this issue-1-reordering branch), and if it works for you, I'll release version 0.6 of the plugin.