PocoDoc: search support

[vrabac6]

The PocoDoc did not support integration with FTS5 SQLite database for the purpose of inputting clean content into the database. To enhance its functionality, the following improvements have been implemented:

1. Expanded the writeDescription method by adding an output stream containing clean content.
2. Introduced a new method named writeSearchIndex , responsible for retrieving textual documentation along with links. This method is called within existing methods writeClass , writePackage , and writeNameSpace

[aleks-f]

• Windows CI is failing; this needs update of vs90 project and regeneration of 160 and 170 projects

  D:\a\poco\poco\PocoDoc\src\DocWriter.cpp(29,10): error C1083: Cannot open include 
  file: 'Poco/Data/Session.h': No such file or directory 
  [D:\a\poco\poco\PocoDoc\PocoDoc_vs170.vcxproj]
  Error: Final attempt failed. Child_process exited with error code 1```

• to prevent sanitizer CI failures, either pick these changes or simply merge devel branch
• search support should be a runtime option
  • there should be a command line parameter added to PocoDoc to generate searchable SQLite DB
  • obviously, a precondition is SQLite built with FTS support
  • there should be a way to check at runtime if Data/SQLite supports FTS; only if it does can searchable content be produced (otherwise runtime error if searchable cmd line param was give)