Build a prototype

[dashohoxha]

Build a prototype of the application, which shows how the final application is going to look like, how it is going to work, the features it is going to have etc. This prototype is not going to be fully functional, for example not doing any gpg stuff yet.

Subtasks:

• Get to know very well how egpg and gpg work.
• Research and test GUI libraries and decide which ones to use.
• Think and discuss about the features and functionality that should be implemented. Maybe design any mockups as well.
• Write the code of the prototype. Several iterations may be needed to make sure it looks ok, getting any feedback from the others as well.

Related tasks: #1, #3, #5, #6

[sourabhtk37]

@yugeshk Since you have completed some of the tasks. Please make sure to tick them off.

[yugeshk]

Ported the basic layout under the Application Framework. For now, that code is under the gui-devel branch. There are two more changes (that I have in mind) I need to make before making a pull request.

[yugeshk]

Added a few mocks of some independent components that can be merged directly with the main UI under mockups folder like Treeview with TreeStore (for contacts).
Wrote a few types of menus though the Application framework has its own menubar structure.