Project Manager: make context-sensitive shortcut menu

[GoogleCodeExporter]

The following relates to the shortcut menu when item is selected in Project 
Manager:
  * Change “Show File” to “Open”
  * Change “Show Map File” to “Show Map”
  * Change “Add File Copy” to “Add Copy of File”
  * Change “Add File Link” to “Add Link to File”
  * Change order of shortcut menu to...
     * Open
     * Show Assembly
     * Show Map
     * Add Copy of File
     * Add Line to File
     * Add Include Path
     * Add Library Path
     * Delete
  * Make the above changes to the Project menu as appropriate.

The following relates to the shortcut menu when no item is selected (blank area 
is clicked) in Project Manager:
  * Should only contain…
     * Add Copy of File
     * Add Link to File
     * Add Include Path
     * Add Library Path
     * Delete

Disable invalid items
  * For example, right-clicking a header file and selecting Show Assembly indicates that this cannot show for this item.  It would be better for the option to not be available in the first place.

Original issue reported on code.google.com by jmar...@parallax.com on 13 Oct 2013 at 7:20

[GoogleCodeExporter]

Text changes such as this impact translations and should be done as a group. 
This will not be addressed until arrangements can be made with translators.

Original comment by jsden...@gmail.com on 2 Feb 2014 at 4:17