Fix for lucene escaping of wildcard

[nickmasster]

Fix for the issue #205.

Probably, there are other servers based on MusicBrainz where escaping is properly supported.

So I've added a method to enable full lucene escaping. By default there's no escaping of wildcard chars. Also fixed the issue in strict mode.

[alastair]

Thanks for this patch.
Please make sure you use -s to sign off commits (https://github.com/alastair/python-musicbrainzngs/blob/master/CONTRIBUTING.md)

I wonder if a global setting is the best way to do this configuration. Another option would be to have it as a per-method flag for each search method. e.g.

def search_artists(query='', limit=None, offset=None, strict=False, escape_wildcards=False, **fields):

where the escape_wildcards field chooses this setting.

We could also consider whether this is actually the incorrect behaviour for the API and wildcards should never be escaped. We could change the documentation to remind users to escape any use of wildcards manually. This however would be a breaking API change.