Issue #262

As per Issue #262, adding a blue info box to the SMTPAPI Apps page, explicitly stating that unlisted apps cannot be updated via SMTPAPI.
made changes to this page to include info on the stats provided in marketing email app.
converted to table for internal consistency
Update php.html

Updated to specify total message size allowed.
Merge pull request #265 from jaysonsperling/patch-3

Update php.html