Bug 10777: email HTML reports with the proper Content-Type

Bug 10777: email HTML reports with the proper Content-Type

The misc/cronjobs/runreport.pl allows for sending html reports
via email. The problem is that the Content-Type isn't set to
text/html, which means that the generated html email isn't
displayed properly.

This patch set the Content-Type, and also adds a tiny bit of
CSS to potentially alternate row colours (just to make long
reports a bit easier on the eye!)

TEST PLAN
----------
1. Run the script similar to this:
    ./misc/cronjobs/runreport.pl --format=html --to=YOUREMAIL --subject="Bad Formatting!" REPORTNUMBER
2. Look at the email - the html code should by visible and ugly.
3. apply the patch
4. Run the script again.
5. Look at the email - the data should look nicer now.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 25076dec54f06b6a7938f4a6cda0a80a1d3d51e4)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>