Fixed drag and drop code to use FileList.getSelectedFiles() instead of
the visible DOM elements.

Now using _.bind() for event handlers so we can use "this" which is more
readable than a static access to FileList.

The file selection is now based on the internal model array
FileList.files instead of the visible checkboxes.

This makes it possible to virtually select files that haven't been
rendered yet (select all, then deselect a visible one)

Added more unit tests for selection (with shift and ctrl as well)

Removed "insert" flag, inserting is by default for FileList.add().
Added "animate" flag to FileList.add().
Added logic to correctly detect when to insert/append elements whenever
the insertion point is visible or not.
Fixed "render next page" logic to work correctly when many pages of
files have been added.

The FileList.files model is now updated with file operations.
Adding files to the list will add to the model first, then to the DOM.
If the insertion point isn't visible yet, the file won't be added to the
DOM until the user scrolls down.

Updated unit tests to include checking for the correct insertion point.

- moved file selection code to FileList
- fix selection summary when all files are selected
- nextPage now auto-selects files if "select all" checkbox is checked
- fixed trashbin to use the same selection logic as FileList

- moved the summary code into a new class FileSummary
- FileSummary is calculated only once, then updated with add/remove
- added new OC.Util namespace for JS utility functions

Will close #8070

Directories will not be considered to have an extension, even if a dot is
found.

Stop Scrutinizer being annoyed

But the spaced version looked good!

Stop jsHint being annoyed

These code quality tools are really pestering

some fixes to make the gallery work, this made it necessary to adjust some tests and the encryption code