incorporated vcard-export patch

from here:
https://github.com/webos-internals/patches/blob/webos-2.2.4/contacts/contacts-enhanced-contacts-vcard-export.patch
Those patches are released under a MIT license.
It fixes an issue with URL field and adds relations to export.
added escaping to VCardExporter

according to RFC6350 all values have to escape
COMMA, SEMICOLON, BACKSLACH and NEWLINE.

So I added that to all values.
imporved unescaping in VCardImporter

according to RFC6350 all values have to escape
COMMA, SEMICOLON, BACKSLACH and NEWLINE.

So I added that to all values where it was missing.

Signed-off-by: Achim Königs <garfonso@tratschtante.de>
allow to supply Person instead of getting it from DB.

Allows third party apps to convert their contacts into vCards,
not the whole person.
allow to read/write to memory by supplying custom reader/writers

Makes processing vCard data from 3rd party servers easier,
also extracting vCards to sync with 3rd party servers gets easier.
improved naming of helper function
Merge pull request #1 from Garfonso/improve_use_cdav

fixes vCard import/export and makes it usable without filewrite