Fix: IDs generation.

Now, ID generator generates IDs from 2. For example: if you start new game, 1st UFO will marked as 2nd (UFO-2).
This fix starts generating IDs from 1 for all objects of new game.
But old games keeps IDs of objects, which never existed (for example AVENGER-1). Therefore, for old games, some IDs will start from 2.