Bugfix for SMTP gateway. (#1482)
Use shorthand notation (code consistency).
For consistency, also change the Sendmail gateway.

Although the Sendmail gateway does not need these changes to work correctly (since it does not have persistent connections), we try and keep the general improvements consistent across gateways.
Bugfix: Recipients formatting slightly incorrect.

Testing for a missing name failed, so email addresses were written in angle brackets (to the "To" header field value) anyway.
Whitespace cleanup.
Merge pull request #1486 from michael-e/fix-core-email

Fix core email API. Closes #1482
Release 2.3.1RC2
Only migrate passwords if there is no updater available
Modularize upgrade-checking a bit
PHPDoc @since
Add filter in created pages

I forget to add the filter in the View all entries link after a creted
a new page.
Merge pull request #1493 from 6ui11em/my-symphony-2

Add filter in created pages. Closes #1421
Merge branch 'hashingmigration' of git://github.com/nils-werner/symphony-2 into nils-werner-hashingmigration
Merge branch 'nils-werner-hashingmigration' into integration
Apply prepopulation/filtering to the Breadcrumbs and Create New links consistently. Closes #1421
Issue #1445 Page Types in the Param Pool
Check Front-End-Https header for __SECURE__ env

Check the Front-End-Https header when determining whether or not the
connection is secure to allow Symphony to exist behind an HTTPS
downstream proxy.
Merge pull request #1497 from designermonkey/page-types-params

Add Page Types to the parameter pool. Closes #1445
Make sure file exists.
Change to X header

Change the downstream-HTTPS switch to X-Forwarded-Proto