Added framework for retroactively enabling checksums on datastreams.
Substantially completed adding ability to retrocatively enable checksums; testing required.
Made testing safer.
With @ruebot's appoval, removed safety logic added in b38b209.
Added wording to README.md about retroactive enabling.
Fixed coding style error in admin.form.inc.
Merge pull request #3 from mjordan/7.x

Add ability to retroactively enable checksums