Add a tool to browse the IMO

[ziotom78]

This PR implements a simple browser for the IMO. It is meant to provide a quick way to copy paths to objects and UUIDs to the clipboard, and it is not meant to be an alternative to the full web-interface to the IMO that is being developed.

I decided to implement a text-only interface, so that the tool can be used seamlessy even when connected through ssh to a remote machine. The curses interface uses Asciimatics, which supports Linux, Mac OS X, and Windows.

Here are the features that are currently implemented:

• Basic text-mode interface implemented using Asciimatics
• Ability to copy paths and UUIDs to the clipboard using Pyperclip
• Add a section about the tool in the User's manual

[ziotom78]

Here is a screenshot:

Note the presence of the «Copy path» and «Copy UUID»: they work on the data file that is currently selected.

I plan to merge this PR soon, as the feature it adds does not clash with anything else in the framework.