Web Monetization fixes + exclusive content

Ref T770

Final API changes

This forces xgo to use Go 1.15, to work around a bug with Go modules:
https://github.com/techknowlogick/xgo/issues/109#issuecomment-835494720

This also uses the correct Darwin and Windows binary names to prevent
failures in the `make release` process.

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Draft list paging

Minor WYSIWYG and miscellaneous fixes

This fixes logging in when developing on newer versions of Chrome.

Fix Gopher links and add blog info

Support international domain names

This file is compiled from other sources, and thus shouldn't be
included in the repo.

Ref T727

Ref T727

T319 user delete acct

Ref T401

T319 admin delete acct

Previously, if running an instance on e.g. http://localhost:8080, the port
would show up in the Gopher links and potentially cause rendering to fail.
This fixes that.

This internally converts the configured host name into its Punycode ASCII
representation, while showing users the correct Unicode domain name.

This adds a configuration option to the [app] section: open_deletion. When
true, users can delete their account on their own.

Ref T319

Ref T319

This requires admins to generate a new encryption key with:
  writefreely keys generate

Ref T319

This mimics the admin UI for deleting a user account.

Ref T319

Ref T319

Ref T319

Ref T319

Disable Ace editor on touchscreen devices

Accept general text/* files on post import