Redo how the repository keys are stored.

- Repository keys are now stored in a new directory on metadir (/var/db/xbps):

	<metadir>/key>

- Repository keys are stored with the hex fingerprint of its RSA
  public key in a plist dictionary:

	<metadir>/keys/xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx.plist

- Drop xbps-rkeys(8) and merge its functionality into xbps-install(8) and
  xbps-query(8).

- xbps-query(8) -vL now shows some more details of remote repositories:

 3134 http://localhost:8000 (RSA signed, verified)
      Signed-by: Void Linux
      4096 60:ae:0c:d6:f0:95:17:80:bc:93:46:7a:89:af:a3:2d
   16 http://localhost:8000/nonfree (RSA signed, verified)
      Signed-by: Void Linux
      4096 60:ae:0c:d6:f0:95:17:80:bc:93:46:7a:89:af:a3:2d

Bump XBPS_API_VERSION.

NEWS

@@ -13,17 +13,15 @@ xbps-0.27 (???):
 
  * xbps-rindex(8): added -v --verbose option.
 
- * xbps-rkeys(8): new utility to manage RSA public keys from remote signed repositories.
-
  * Support for RSA signed repositories. A repository can be signed with your
    preferred RSA key (any ssh key works) as follows:
 
 	$ xbps-rindex --sign --signedby "foobar <foo@bar>" --privkey /priv/key /path/to/repo
 
    Public keys must be imported before using a remote signed repository thru
-   the xbps-rkeys(8) utility:
+   the xbps-install(8) utility:
 
-	$ xbps-rkeys -i <repourl>
+	$ xbps-install -S
 
    Once the public key has been imported it's not expected to change, hence if the
    repository index has been modified or signed with another key, it will be ignored.