Update bypass_list_management.md

Add info at top - this app available for Silver and higher
Merge pull request #676 from bhammerquist/patch-4

Update bypass_list_management.md
Update forward_spam.md

Added warning at top - available for Silver or higher
Merge pull request #680 from bhammerquist/patch-8

Update forward_spam.md
Merge branch 'develop' of github.com:sendgrid/docs into develop
Items #510, 512, 514 & 516
Itmes #517 - 526