[Design] A new logo.

I asked designers to produce a new logo for the application in order to align it more close to the official JBoss Developer family.

- New logo image
- Minor change in background color
[Author filter] Move to new general list filter implementation. Closes #81

Disabling search field in Author filter because we do not have any public suggestions API for it now (see https://github.com/searchisko/searchisko/issues/125).