[ui] Modal dialog too small for complex object creation

Using modal dialog for object creation doesn't suit Hue very well. The window is too small. (See the attached video.) Problems include:

• The window is too small. Lots of scrolling and lack of overall context.
• Certain fields give yet another popup. A popup within a popup is too much. And note that the file chooser popup doesn't entirely steal the mouse.
• When the file chooser popup is closed, the modal dialog scrolls back to the top.
• For this form in particular, there are a few submission errors.

Going back to the old way will also make it easier for backend developers to write and debug their forms.