Minor beautification

I've fixed a few typos in Generators/Generator.php and added a missing space in Generators/FormDumperGenerator.php.

Also, i noticed that sometimes you put fullstops after comments, and sometimes not. For continuity, i've added some fullstops in some files where you were already using fullstops most of the time, but missed a couple. Where you haven't used fullstops at all, I've left unchanged.