various additions/updates

- added a trigger event when the files have their HTML5 preview loaded and displayed
- added a delimiter option which can be used in order to give more than 1 file as a string data-attribute for the initPreview option (initPreview function adapted to that)
- replaced all the hard-coded "files selected" by the option "msgSelected" in order to retrieve my translations given as data-attribute
- Now take in account the number of initPreview displayed when the param "overwriteInitial" is set to false and when we add new files.
- special preview templates in order to create any specific dom element for each file. It is now possible to manage that with options (+added generic template for initPreview)
- creation of an event trigger fired when all files are cleared (by the remove button/top-right cross)
- added disable and enable functions in order to easily disable/enable the fileinput without reloading the html (solve the remove button problem)
- added a width management when images are too wide (now they are scaled by width [height="auto"] if their width is bigger than the container)
- some little fixes