Refactored MoreMenuUI service

Refactored MoreMenuUI service

[Issue#]   https://bugs.tizen.org/jira/browse/TT-72
[Problem]  Lots of style fixes, several fixes for build warnings
[Cause]    n/a
[Solution] Reformat code, fix casting and remove unused variables
[Verify]   1. Check that there are no build problems caused by this change
           2. Run the browser and explore the More Menu to see if nothing's broken

List of changes:
* tabs -> spaces
* proper indentation
* other minor style fixes
* removing unused variables' declarations
* renaming a few class members to better express their use
* replacing reinterpret_Cast with static_cast where appropriate
* adding null-checks in callback functions
* replacing shared_ptr copy-assignments with make_shared

Change-Id: I6a65bbcf9efaef42db955c689ba81673cb12e1fa