Material design + view related refactoring

 - Material design
 - New light theme
 - Theme switcher
 - Full layout refactoring
 - Dialogs refactoring
 - Search view in track list

TODO:
 - ~~Fix switch "track" color (now it's invisible when switch is of in light theme)~~
 - ~~Scroll bar missing in track list~~
 - ~~Upload new screenshots~~
 - ~~Find out what's wrong with unit tests and fix them~~