fixed escape handling in SQLIdentifier and added tests

About half a year ago I created a pull request [1] which was rejected for some reasons. It took some time to take a deeper look at this since I reduced my time at office (to enjoy the similar-to-me-looking result of a merge and fork process...).
I found two causes that prevent escping to work:
1. SQLIdentifier.getName() returns the string stripped of escaping characters
2. The grammar does not allow escape characters in identifiers
So I added the escape characters to the getName() method and also allowed quotes in identifiers.

Kind regards,
Jeronimo

[1] #198