Fix: docs: guides: certificates: update to the v3 filenames

the "PEM Bundle" file and copy it to your Onionspray server.  Also: copy the

`privateKey.pem` file (mentioned above) to the Onionspray server.

Next, change Directory into `~/onionspray/projects/PROJECTNAME.d/ssl.d`; you

should see your development certificates, which will look like:

Next, go to `~/onionspray/projects/PROJECTNAME/ssl` folder. There you should

see the development certificates, which will look like:

    $ ls

    ONIONADDRESS.onion.cert

    ONIONADDRESS.onion.pem

    SHORT_ONIONADDRESS-v3.onion.cert

    SHORT_ONIONADDRESS-v3.onion.pem

where `SHORT_ONIONADDRESS-v3` is the same as the name of the address subfolder

under your project, e.g. `foo13majanhxc6x-v3`.

There are two steps to installation:

* Step 1: copy the PEM Bundle file from HARICA, on top of `ONIONADDRESS.onion.cert`

* Step 1: copy the PEM Bundle file from HARICA, on top of `SHORT_ONIONADDRESS-v3.onion.cert`

* Step 2: unlock and extract (or rename) the private key, by doing:

        openssl ec -in privateKey.pem -out ONIONADDRESS.onion.pem

        openssl ec -in privateKey.pem -out SHORT_ONIONADDRESS-v3.onion.pem

... and typing in the password that you chose during the CSR setup, earlier; if

you chose to use RSA as the algorithm, you will need to use `openssl rsa ...`

instead.

If you manually created the CSR, then rename the 'onionaddress.key' file the

CSR generated to `onionaddress.onion.pem`.

If you manually created the CSR, then rename the `SHORT_ONIONADDRESS.key` file the

CSR generated to `SHORT_ONIONADDRESS-v3.onion.pem`.

Then: change directory back to the Onionspray directory, and do `onionspray

nxreload projectname`, and test it.