v0.12: view refactoring has started

New:
0) code of AbstractPage and MainPage is refactored
1) navbar
2) icons
3) tables
4) pages

To Do:
1) pages "pre" and "next"
2) bean "Project" is still absent
3) view refactoring (IssuePages)
4) performance refactoring
5) add future pages
6) ...