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/osx.plugin.bash

@@ -1,6 +1,10 @@
-#!/usr/bin/env bash
+cite about-plugin
+about-plugin 'osx-specific functions'
 
 function tab() {
+  about 'opens a new terminal tab'
+  group osx
+
   osascript 2>/dev/null <<EOF
     tell application "System Events"
       tell process "Terminal" to keystroke "t" using command down
@@ -15,6 +19,10 @@ EOF
 # this one switches your os x dock between 2d and 3d
 # thanks to savier.zwetschge.org
 function dock-switch() {
+    about 'switch dock between 2d and 3d'
+    param '1: "2d" or "3d"'
+    example '$ dock-switch 2d'
+    group osx
 
     if [ $(uname) = "Darwin" ]; then
 
@@ -39,6 +47,10 @@ function dock-switch() {
 # Download a file and open it in Preview
 
 function prevcurl() {
+  about 'download a file and open it in Preview'
+  param '1: url'
+  group 'osx'
+
   if [ ! $(uname) = "Darwin" ]
   then
     echo "This function only works with Mac OS X"