improve attack group composition

base attackcounter on unit techlevel
further limit production of tacnukes--two or three is already a bit
much, and sometimes over five get built
fix problem: too many vulnerable siege units in attack groups
don't build breakthroughs until there's a reasonable number of regular
battle units--building a goliath, a krogoth, or a bantha right off the
bat is a bad plan
encourage raider clumping

- build slightly more siege units
reduce targetting threat threshold for raiders near other raiders
reduce threat of cells with raiders in them or targetted by raiders for
other raiders, so that they will tend to join nearby raiders
only revert to building lvl1 if metal is *really* high (95% of capacity
or more)
prevent raider donutting

make commanders run away less easily
increase slightly the threat of targets along the way to which raiders
or scouts encounter threats, using very weak bad position records
Merge pull request #38 from zoggop/master

BA: improve attack and raid