Documentation fixes & improvements

[MangoMarcus]

Various documentation fixes including:

• Invalid types (typos or incorrect namespacing, e.g. PDOStatement missing leading slash)
• Incorrect types (i.e. valid but incorrect types)
• Typos in descriptions
• Nullable types
• Missing @param and @return tags
• Replaced some references to classes with their corresponding interface where appropriate (eg. where dependency injection is supported)
• Improved typing of arrays, eg. OODBBean[] instead of array (see PHPDoc documentation)

These changes help static analysers identify problems and make suggestions. For example, using @return OODBBean[] can provide type information even when iterating:

foreach ( R::findAll('book') as $book ) {
  // IDEs now know $book's type and can make suggestions like auto-completion or help with method signatures
}

[gabordemooij]

Awesome! Thank you very much!