From now on, all English strings use the new syntax. They are not
eval()'ed any more and the only valid placeholders are {$a} and
{$a->foobar}. No extra quotes escaping, dollar sign escaping and putting
double percent signs.

The modified files were exported from AMOS database repository in the
new syntax and were re-ordered by stringid. Standard GNU/GPL and PHPdoc
blocks are added. Where there was no copyright note so far, I added the
default one with Martin Dougiamas as the copyright holder.

Live long and prosper.