Updated changelog for 7.x-1.2
Issue #2237585: Make allowed file extensions for attachments configurable
Issue #2368533: Bypassing views render layer breaks all sort of things
Renamed internal helper function.
Issue #2693393: Mailsystem 3.x-dev requires "key" and "module" keys in the mail message
Improved messages about token replacement.
Improved help for tokens in general and fixed help for tokens from Token module (no longer using _theme).
Fixing redirect after completed batch job.
Fixed (Views Send specific) token replacement.
Fixing help for tokens (no longer using _theme and hook_theme).
Fixing config saving ("remember these values") and hiding of output.
Replaced watchdog with \Drupal::logger - ref https://www.drupal.org/node/2270941
Some field object fixes.
Various D7 to D8 fixes - OOP stuff mostly.
$form_state is now a classed object - removed all (?) array usage.
Added libraries.yml for CSS file (used in $form['#attached']['library']).
Replaced l() with \Drupal::l()
step and rebuild (in FormStateInterface) aren't form values - don't use value functions.
Some leftovers after the introduction of FormStateInterface
Introduced FormStateInterface in Views plugin too.
Replaced hook_permission implementation with permissions.yml
Removed old D7 cleaning of cache/variable table after uninstall.
Use getValue() to get values from which is an ConfigFormBase object.
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