Round a Float in the bylaw text to two decimals

[Thayorns]

Since #992 a let in a bylaw can hold a computed value, and Fbe::Award::Bylaw#line printed it with plain interpolation. So a bylaw could say "award 0.30000000000000004 points" or "0.3333333333333333", as #1220 shows.

Now a Float in ${...} of a bylaw line is rounded to two decimals, and the fraction is dropped when it is zero, by a private short in Bylaw. That is the same rule #1219 proposes for the text of a bill, so both sides of one policy print a value the same way. Integers and Strings are printed as before.

The new tests cover 0.1 × 3, a third, a random negative rate, a whole Float and a tiny negative Float.

Closes #1220

[Thayorns]

@yegor256 take a look please, happy to clarify anything about this change.