New Sector hangs on sector size 38x38 or greater

[nboughton]

Reproduce:

swnt new sector -l -e 38 -w 38

Sector creation succeeds at either version 37x38 but hangs on anything greater. The number of cells created in 37x37 is 1406, whereas the next increment produce 1444.

[nboughton]

The problem is name.System. The current list has 501 items however the number of cells occupied on a 38x38 map is

cells := s.Rows * s.Cols
stars := (rand.Intn(cells/4) / 2) + (cells / 4)

This is will be more than 501 and as the names picked must be unique a loop occurs when it can no longer find unused names.

Solution:
Write a name generator so that no such limit occurs.

[nboughton]

Commit 98ce744 implements a primitive name generator that can improved later.