upload-modal: better name for file input
upload-modal: fix adding files without debug info (fixes #194)

Before we were using angular.element(this).scope() to get hold of the
current scope and then invoke the fileSelected function. This was ugly
and doesn't work when debug info has been disabled.

We now use a tiny directive instead for a much cleaner solution.
sbOnChange: handle $apply inside directive

This moves the complexity away from the caller.
sbOnChange: call event handler like a normal event handler

This means setting this to the target element and passing the event to
the handler.
Merge pull request #196 from mgeisler/upload-without-debug

Fix file upload when debug info has been disabled