SFTP filebrowsing

[Yuri Samoilenko]

> and also added a function that returns the
> mount point to the sftp plugin, so setting it as a property is not
> needed anymore and I removed that. I hope you don't mind that, I think
> it was only used for that reason, am I right?
>
> Check it out and say me if it works for you :)

I plan to make multiple mountpoints for single device in future: for
files, for images or othe medias, and I planned to create multiple
KProcess of sshfs each with own mountpoint. I'am not think a lot about
it.

I have counterquestion:

I want to remove keys from config files as descrbed in TODO in
device.cpp, and put it with very strict permissions(like ssh id_rsa)
into kdeconnect application directory(~/.kde4/apps/kdeconnect/key.pem
and key.pub).
Also device holds only publicKey(with bug?) by now and passed
privateKey only to deviceLink. But sftp-plugin needs private key to
make sshfs work and I think to store private key into device and add
possibility to provide it to plugins.