Packaging, new filter options and syntax check

[kkaris]

This PR does four things:

• Checking the syntax of the curation comment depending on source. If activated, the syntax check is done at submission time and returns a 422 with error text describing the issue if the text is invalid.
• Filter out already curated statements. This resolves Flag for filtering statements that already have curations #8.
• Search box that filters based in the english assembled text of each statement.
• Restructure repository for packaging

This PR also includes minor updates to Vue/JS code to remove warnings and errors as well as some smaller style fixes.