Upgrade mySQL 5.6 to 5.7

[sashadev-sky]

Current status: Ruby 2.4.4, Rails 3.2, mySQL 5.6
Moving to: Ruby 2.4.4, Rails 3.2, mySQL 5.7

additional points:

• delete mapknitter/config/initializers/new_rails_defaults.rb along with upgrade
• fix PR template to include a reference # prompt
• Address Ruby warnings
• Other small fixes, etc.

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[sashadev-sky]

closed via #355