UI/UX Improvements

* Added dblclick edit and longclick preview to dragitem
* Added menu transparency
* Added scroll prevention when using the modal or dragitem navigation
* Added plugin info within edit-modes tooltip
* Enabled sortable to be canceled using "esc"
* Improved menu dropdown styles
* Improved plugin draggable visibility
* Improved expand/collapse all and moved to left
* Improved toolbar lock visibility
* Fixed issues with toolbar overlapping content using margin offsets
* Fixed issues with menu hover and click events
* Fixed issue with preventDefault and javascript events
* Fixed issue with modal resize when scrollTop is larger than 0
* Fixed issue where preventSubmit affects the entire site
* Fixed DjDT position while using the toolbar
* Fixed issues with djangocms-admin-style
* Disabled scrollTop auto jump (will be obsolete later)

fixes issues:
#2261

possibily fixes
#2163
#2128