Remove paragraph with wrong claims about BUILD
Remove paragraph with wrong claims about BUILD

replace it by something that clearly states that
BUILD, TWEAK and BUILDALL are called on instances,
and mention that virtual method calls in there are
not a terribly bright idea.

Closes #1459

stmuk/doc,jonathanstowe/doc,antquinonez/doc,perl6/doc,dmaestro/doc,antquinonez/doc,tbrowder/doc,antquinonez/doc,dmaestro/doc,jonathanstowe/doc,perl6/doc,gfldex/doc,tbrowder/doc,MasterDuke17/doc,stmuk/doc,gfldex/doc,jonathanstowe/doc,MasterDuke17/doc,dmaestro/doc,tbrowder/doc,antquinonez/doc,MasterDuke17/doc,perl6/doc,perl6/doc,stmuk/doc,stmuk/doc,gfldex/doc,gfldex/doc,perl6/doc,MasterDuke17/doc,dmaestro/doc,dmaestro/doc,jonathanstowe/doc,stmuk/doc,tbrowder/doc,gfldex/doc,jonathanstowe/doc,antquinonez/doc