refactor WebGUI.Admin.prototype.gotoAsset slightly to avoid code duplication
WebGUI.Admin.prototype.addPasteHandler: guessing but fix use of 'this' vs 'self'
currentTabName() to avoid code duplication for figuring out which context we're running in (Tree/View)
WebGUI.Admin.prototype.pasteAsset:  handle pasting in the Tree view by flopping over to the View view first
removed WebGUI.Admin.Tree.prototype.runHelperForSelected and relatedly WebGUI.Admin.Tree.prototype.cut, copy, shortcut, duplicate, delete; these are dead code
WebGUI.Admin.Tree.prototype.goto: better error handling/debugging
added this FIXME to WebGUI.Admin.prototype.gotoAsset:
a lot of Tree view operations fail after this point.  where the View version just directly goes to the URL, the Tree view tries to modify the URL to pass the extjs-style grid's parameters back.  this winds up creating unworkable URLs that try to do two things at once, with two '?'s, two 'op='s, etc.  there are two ways to fix this:  if we're trying to go to an asset (gotoAsset) and we're in Tree view, flop back to View mode first; or else two distinct requests, one for the remote request (which might generate additional requests to draw in dialog boxes, progress bars, forms, etc) and then when that's all done, refresh the grid view.  WebGUI.Admin.prototype.pasteAsset takes the route of flopping to Tree view first.