Exposed class methods to be public, added support to insert HTML to selected columns via appendHTMLSelectedCols, added ability to select columns by clicking on them
Added new selectable columns, new API method to insert HTML and relevant CSS
small tweaks to merge

Changed colSelected to gm-editing-selected for consistency;
Made onClick non bootstrap dependent
Changed CSS border to inset shadow red
Remove additional editing classes on deactivatecols

gmEditClassSelected needs to be stripped out on preview