WIP openemr#7480 openemr#7494 email prescriptions

Currently a work in progress.  This supports sending a prescription as a
pdf to an email address, sending the prescription inline as a formatted
html email, and sending the prescription in the native mail client using
the mailto: protocol.  Mailto: doesn't support email attachments so the
pdf option currently doesn't work with this.

I've looked at potentially generating an EML file that will have the pdf
file inlined to support that sending option.  If that doesn't work I'll
need to disable the pdf option when the Use Default Mail Client option
is selected.

When the Default Mail Client is selected (openemr#7494) then the mailto link is
generated and if the browser or operating system has a mailto: protocol
handler setup it will launch the registered handler with the subject and
email body populated.

I need to test on prescription lists greater than 3 (for handling with
paginations).

I also need to make sure I haven't broken any of the faxing and other
prescription sending functionality.

Also, if anyone has customized these views this will have an impact on
them so putting this PR out there for people to comment on as needed.