Internal improvements 5

[blocknotes]

Internal improvements:

• Upload: add configurable max file size guard;
• add UNPROCESSABLE_STATUS constant;
• DBServiceRails70: use select(:data) to avoid loading full AR objects;
• minor update in DbService;
• minor update in gemspec;
• rake tasks minor improvements;
• update schema.rb sorting columns by name.

[epugh]

Just wanted to share I am a BIG FAN of this gem, it's been key to github.com/o19s/quepid..... Thanks for doing the work to keep it up to date.