[Xon] Search Improvements 2.17.0

• Cleanup add-on description & readme file
• Update XFES dependent option descriptions to include if they require XFES
• Improve styling of 'no results' search result in an overlay
• Fix search result terms do not display when search results are in an overlay
• Fix custom styling triggering "Your changes have been saved." when clicking a member search link

• Fix "Push "View X by others" option being disabled would cause some user information to not be indexed, which had the implicit "rebuild search index" if this setting was then enabled.
  • This fixed conversation search when using Conversation Improvements v2.4.x+
  • Requires a re-index of at least conversations/conversation messages to re-add the missing information.
  • For most sites, disabling the "Push "View X by others" check into XFES" option is not recommended

• Fix error "Object of class XF\Mvc\Reply\View could not be converted to string" when a user is denied search tries to use search

• Fix additional XFES index page would show even when XFES was not installed/active

• Fix searching by member without a keyword for a guest

• Fix cached search results would be unexpectedly be viewable to anyone if they guessed the search result URL.
  • Affected versions; v2.8.1
  • These search URLs expire after a day
• Fix search term on search result pages leaking information for non-viewable content
  • Affected version; v2.7.4, v2.7.5 and v2.8.1
  • Fix leaking thread title when using "In thread" search area, and rendering a bad phrase if the thread doesn't exist
  • Fix linking to non-active user profiles when searching by members
• Workaround for an XF bug where the cached search results for a member search could be directly shared with a guest
  • Non-visible items on the result page where not rendered, but this does leak that there are hits in not viewable to guests areas.

• Fix "before" search result term would print an integer instead of a human readable yyyy-mm-dd formatted string
• Change 'no results found' handling to display search terms on the relevent page
  • If using ElasticSearch Essentials, recommend updating to v3.13.0+ as this change may impact some options which display on no results found.
• Fixes for search term on results page
  • Add missing "With X thread" search term
  • Fix "Users" search term could fail to render the list of usernames
  • Add the 'content type' search term

• Remove usage of utf8_* function(s), and use native php multi-byte functions instead.
• Fix HTML markup error in svPushViewOtherCheckIntoXFES option description

• Fix bug where 'weight by content type' feature didn't work as expected in general search
• Thanks to @NamePros for sponsoring this update.
• Display various search term constraints on the search results form.
  For developers to implement support in 3rd party add-ons:
  • Each search constraint needs a svSearchConstraint. prefixed phrase.
    Arrays are mapped to phrases by adding a _ for each sub-array/key as such; c[warning][points][lower] => svSearchConstraint.warning_points_lower
  • Each search order needs a svSearchOrder. prefixed phrase.
  • Extend XF\Entity\Search::getSpecializedSearchConstraintPhrase(string $key, $value) to provide custom phrase handling (ie node names)
  • Extend XF\Entity\Search::formatConstraintValue(string $key, $value) to provide custom formatting.
  • Extend XF\Entity\Search::setupConstraintFields to populate $svDateConstraint/$svUserConstraint/$svIgnoreConstraint properties which control formatting
• Use the debug option "List all unphrased search constraints" which will dump unmapped contraints to search results page.

• Fix incorrectly adding a return type to XF\Search\Search::isValidContentType
• Fix typo in admincp options phrase