Add print options supports - staff can now print a ticket thread without internal notes + select paper size on the fly

Rather than defaulting to either showing answered tickets or closed tickets
if there are no open tickets.

And correct several undefined function errors from several source files. So
while function names in PHP are considered case-insensitive, it still makes
sense to use consistent camel casing for both defining and calling methods.
The lint test searches the code base for method calls, and then searches the
code base again looking for a function definition matching the name of the
function invoked. It's not failsafe, because it doesn't detect the class
from which the method should belong, so it's likely to have false negatives.
Furthermore, it won't work well for PHP 5 where several classes are built
into PHP (and aren't searchable in the osTicket code base).

Remove the include/staff/api.inc.php as it no longer appears to be used (and
contains references to undefined methods).

Adds a link to the scp/tickets.php page (Tickets) allowing for the export of
the data to CSV file. This is preliminary and still needs a few items:
  * An icon + button CSS definition
  * Support for alternate columns (staff assigned, etc.)

Also add beginnings of complex export support (PDF, JSON  and other
formats
to follow). CSV is fully supported for now.

And for brevity, add a Http::download method to allow for consistent and
browser-independent forced page content downloads