Test allowedExtensions in UploadField, return correct HTTP status
FIX preg_replace_callback in emailer was broken

Fixes bug introduced by 9deb11f9a0ee01477af38f2826b2a7583545a0b6
Email has no content
This is what happens when we make commits without testing!
Merge pull request #2229 from ss23/patch-6

FIX preg_replace_callback in emailer was broken
BUG First error should take precedence here. No further checks needed.
Merge pull request #2244 from mateusz/lockout-errors

BUG First error should take precedence here. No further checks needed.
FIX Prevent DOS by checking for env and admin on ?flush=1 (#1692)
Merge pull request #2243 from hafriedlander/fix/flush_30

FIX Prevent DOS by checking for env and admin on ?flush=1 (#1692)
Merge branch 'origin/3.0' into 3.1
FIX: Have ParameterConfirmationToken work regardless of include path
FIX: Ignore invalid tokens instead of throwing 403
Merge pull request #2248 from hafriedlander/fix/flush_30

FIX: Have ParameterConfirmationToken work regardless of include path
Merge branch 'origin/3.0' into 3.1
Versioned documentation typo (Thanks aragonne)
Split Core.php into Constants.php and Core.php and adjust main.php startup

The recent flush filter fix had a problem that you couldnt set a custom
BASE_PATH in _ss_environment because that file didnt get included until
after checking the confirmation token. This patch pulls the part of Core.php
that defines BASE_PATH into a seperate file that can be included earlier
in the startup sequence so that ParameterConfirmationToken can access it.

Core.php includes Constants.php with a require_once call, so for startup
scripts that dont pull in Constants.php themselves (like cli-script.php)
no change is needed.
FIX Only suppress fatal errors
Merge pull request #2255 from hafriedlander/fix/flush_30

Split Core.php into Constants.php and Core.php and adjust main.php startup
BUG Fixed divide by zero with SetRatioSize on missing image file
Fixes issue #2047
Merge pull request #2256 from tractorcow/3.1-setratiosize-dbz-fix

BUG Fixed divide by zero with SetRatioSize on missing image file
Fixed CountryDropDownField showing East Germany
FIX Nice errors and allows flush on module removal