Added command binding for closing tabs to right

Also moved closeTab() function into a lambda, since it's confusing to
have both it and removeTab(), and the former only works with the context
menu anyway.
Mental note, don't comment out code you want to run.
Bugs in removeTab were keeping closeTabsRight from iterating.
Remove data that's added now that we're using links instead of spans for tabs.
Converting to promises broke File.getPath and thus project file de-dupe.
allow drag-drop opening of files and directories
Merge pull request #125 from mastercactapus/dragdrop

allow drag-drop opening of files and directories
Fixes #121
Bind for file-based DOM events in fileManager, not in command.
Fix bad refactoring.
Simplify tab context URLs -- they're not a heirarchy, they don't need a root path segment.