standardize plugins, update metadata

add about-plugin metadata
chmod -x plugins
cleanup filenames to standardize on x.plugin.bash format
only plugin files intended to be executable from the command line should
contain a shebang line, and should be a+x.

plugins/available/base.plugin.bash

@@ -1,7 +1,5 @@
-#!/usr/bin/env bash
-
 cite about-plugin
-about-plugin generic and miscellaneous tools
+about-plugin miscellaneous tools
 
 ips ()
 {