don't remove \n characters from written po file

in Item.toString, all \n characters are removed from the output.
The gettext tools however leave those characters intact. This
will now produce the same output as tools like msgcat.
Fixed unescaping of all escaped C String characters.

Signed-off-by: Julian Bäume <julian@svg4all.de>

Conflicts:
	lib/po.js
properly escape all unprintable characters

writing messages should no be in line with gettext tools. I tested
using msgcat, it provides the same results.

For some common use-cases I wrote explicit tests, for uncommon and
even unwanted use-cases I wrote one test to make sure pofile works
like msgcat for those messages
Merge pull request #12 from Open-Xchange-Frontend/cstring_escapes

Cstring escapes