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.

bin/xbps-query/xbps-query.8

@@ -175,8 +175,7 @@ Default cache directory to store downloaded binary packages.
 .Xr xbps-pkgdb 8 ,
 .Xr xbps-reconfigure 8 ,
 .Xr xbps-remove 8 ,
-.Xr xbps-rindex 8 ,
-.Xr xbps-rkeys 8
+.Xr xbps-rindex 8
 .Sh AUTHORS
 .An Juan Romero Pardines <xtraeme@gmail.com>
 .Sh BUGS