rc: autogenerate and tidy the docs and commands

* Rename rc/pid -> core/pid
  * Sort the output of `rc list`
  * Make a script to autogenerate the docs
  * Tidy docs

bin/make_rc_docs.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+# Insert the rc docs into docs/content/rc.md
+
+set -e
+
+go install
+mkdir -p /tmp/rclone_cache_test
+export RCLONE_CONFIG_RCDOCS_TYPE=cache
+export RCLONE_CONFIG_RCDOCS_REMOTE=/tmp/rclone/cache_test
+rclone -q --rc mount rcdocs: /mnt/tmp/ &
+sleep 0.5
+rclone rc > /tmp/z.md
+fusermount -z -u /mnt/tmp/
+
+awk '
+    BEGIN       {p=1}
+    /^<!--- autogenerated start/  {print;system("cat /tmp/z.md");p=0}
+    /^<!--- autogenerated stop/   {p=1}
+    p' docs/content/rc.md > /tmp/rc.md
+
+mv /tmp/rc.md docs/content/rc.md