Bug fixes and solution improvements

1) During previous migration to Maven structure and code cleanup there were several bugs introduced. With this pull request I'm supplying fixes for them
2) Support for predefined symbol classes was added. Now we can use \s, \S, \d, \D, \w, \W keywords to generate expressions. Previously it wasn't supported even by Automation library
3) Tests were added to make sure that new changes don't break existing functionality (currently tests provide 80% code coverage)
4) Pom.xml was synchronized with original one in mifmif/Generex repository