First functional version

• Added Executor class with methods:
• MatchResult getAllMatches(string $pattern, string $subject, integer $offset = 0)
• Match getOneMatch(string $pattern, string $subject, integer $offset = 0)
• boolean match(string $pattern, string $subject, integer $offset = 0)
• ReplaceResult replaceAndCount(string $pattern, string $replacement, mixed $subject, integer $limit = -1)
• mixed replace(string $pattern, string $replacement, mixed $subject, integer $limit = -1)
• mixed replaceCallback(string $pattern, callable $callback, mixed $subject, integer $limit = -1)
• ReplaceResult replaceCallbackAndCount(string $pattern, callable $callback, mixed $subject, integer $limit = -1)
• Added Match, MatchResult and ReplaceResult objects.
• Support for Flux and VerbalExpressions
• Errors are thrown as exceptions and not displayed.
• Unit tests added.