ToER update 2020.1

ToER 2020.1 update includes:

1. Arsonist arrows damage is now increased.
2. Mill building should now have correct textures.
3. Selection rectangle should not dissapear when mouse goes over buttons or menus.
4. Units now can't be accidentially selected when menus are open.

ToER 2019 is now the final version in 2019 cycle.