Default operations

[hrstoyanov]

@infeo doakn-java needs some more default handle implementations to be useful standalone. I look at the cryptomator/dokany-nio-adapter code and I think a lot of the implementation stuff can be transferred to this project doakan-java . I made an attempt to do so, (massively cleaning up the code )in the process - see the attached file (as well as the changes I made in #50 ) proxydrive.zip