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-install/state_cb.c

@@ -48,10 +48,10 @@ state_cb(struct xbps_state_cb_data *xscd, void *cbdata _unused)
 	switch (xscd->state) {
 	/* notifications */
 	case XBPS_STATE_REPO_SIGVERIFIED:
-		printf("[*] RSA signature verified correctly\n");
+		printf("[*] %s: RSA signature verified\n", xscd->arg);
 		break;
 	case XBPS_STATE_REPO_SIGUNVERIFIED:
-		printf("[*] RSA signature UNVERIFIED! ignoring...\n");
+		printf("[*] %s: RSA signature invalid! ignoring...\n", xscd->arg);
 		break;
 	case XBPS_STATE_TRANS_DOWNLOAD:
 		printf("\n[*] Downloading binary packages\n");
@@ -130,6 +130,11 @@ state_cb(struct xbps_state_cb_data *xscd, void *cbdata _unused)
 			    "(rootdir: %s).", xscd->arg,
 			    xscd->xhp->rootdir);
 		break;
+	case XBPS_STATE_REPO_KEY_IMPORT:
+		printf("%s\n", xscd->desc);
+		printf("Fingerprint: %s\n", xscd->arg);
+		rv = yesno("Do you want to import this public key?");
+		break;
 	/* errors */
 	case XBPS_STATE_UNPACK_FAIL:
 	case XBPS_STATE_UPDATE_FAIL: