Delete confirmation, new options and style updates

[kevinchappell]

Updated
reduced save and preview debounce timeout
added stopIndex to help with field drops
showWarning becomes fieldRemoveWarn

Added
events.js, file to register events.
field removal confirmation - configurable with fieldRemoveWarn options
close edit button at bottom of all field types
clear all button
append and prepend options. This lets you append or prepend html to the beginning or end of your form to give user's an idea of what the completed form will look like even for fields they cannot edit. Example

Removed
"Form Elements" header of control buttons.

Style updates
field actions moved to top right, delete button style updated. Hover a delete action will turn background of field pink
sortable options restyled
Responsive field attributes

Performance improvements:
update the preview for only the field that was updated.

Notes
instant updates, preview updated faster and save happens whenever a change is made
convert static strings to use _helpers.markup. Currently just flattens out with outerHTML but eventually all for formBuilder elements will have full prototype inheritance.

Numerous improvements were made in this release but more focus in needed on performance in the next couple weeks. Example: when one field is changed, the save cycle runs on the entire set of fields. We should be able to update a single field and have only that fields data node.

@todo: field layout features making use of bootstrap 3 columns