functional interfaces for takes and responses

See #739, release log:

• 08dbc10 by @yegor256: #739 more ctors
• 3dc18a3 by @yegor256: #739 Scalar
• 54461ec by @yegor256: #738 fixed broken links
• d439791 by @yegor256: #733 titles for SPANs
• c384b20 by @yegor256: #735: argline

Released by Rultor 1.66.1, see build log