Merge pull request doccano#670 from doccano/bugfix/enable-to-display-…

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Enable to display non-ascii metadata

Merge pull request doccano#654 from doccano/bugfix/multiline-display-…

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Enable to handle multiline document in sequence labeling

Merge pull request doccano#422 from CatalystCode/enhancement/mysql

Enhancement/Add support for MySQL

Add X-Frame-Options header to prevent clickjacking

Merge pull request doccano#341 from chakki-works/dev-frontend

Supporting mobile annotation