* Work on firming up the plugin interface:

* Work on firming up the plugin interface:
  - Plugins should not need to load IkiWiki::Render to get commonly
    used functions, so moved some functions from there to IkiWiki.
  - Picked out the set of functions and variables that most plugins
    use, documented them, and made IkiWiki export them by default,
    like a proper perl module should.
  - Use the other functions at your own risk.
  - This is not quite complete, I still have to decide whether to
    export some other things.
* Changed all plugins included in ikiwiki to not use "IkiWiki::" when
  referring to stuff now exported by the IkiWiki module.
* Anyone with a third-party ikiwiki plugin is strongly enrouraged
  to make like changes to it and avoid use of non-exported symboles from
  "IkiWiki::".
* Link debian/changelog and debian/news to NEWS and CHANGELOG.
* Support hyperestradier version 1.4.2, which adds a new required phraseform
  setting.