File operation cell button is inconvenient

[glen.low@…]

In most file operation setting screens, the action button is a cell-based button, which makes it inconvenient to activate: you sometimes need to scroll the screen to reach it. It would be better to use a navigation bar button as an action button which can be tapped without any scrolling, especially when the user does not actually need to change any of the settings.

[glenlow]

(In [170]) Added batch file operations in Graphs list: action button on navigation bar; share, duplicate and delete buttons on the toolbar; user can now choose multiple output formats (fix #103). Removed file operations from Graph settings (fix #102). File operation settings now use navigation bar done button instead of table cell button (fix #104). Refactored IVDirectory into IVSortedSet, an NSSet subclass that keeps its elements sorted. Refactored session code into superclass IVSession. Settings view controller now uses single NIB file.