Improve ID random generation

[rokath]

Currently new IDs are randomly generated and afterwards checked, if already used. If, the process starts again. That works fine as long the used ID amount is small. A better approach is, to select randomly from the so far unused IDs.

[rokath]

Joinedxwith #260

[rokath]

Remove "alredy used" message

[rokath]

An init() function should create a uint16 slice with len IDmax - IDmin and fill it iteratively with IDmin....IDmax. Any used ID is swapped to the slice[used] with used++. For a new random ID r use interval [0, len - used]. Then swap slice[used] and slice[used+r], used++ and return original slice[used+r].

[rokath]

If IDs exist outside IDmin...IDmax, they are ignored. If such a trice changed, simply a new ID is generated.

[rokath]

Done in trice insert from v0.61.0