Makefile: change BINDIR from "/usr/sbin" to "/usr/bin"

With "backend btrfs-progs-btrbk" and "backend btrfs-progs-sudo", btrbk
does not necessarily need to be run as root.

Makefile

@@ -23,7 +23,7 @@ PN         = btrbk
 PREFIX    ?= /usr
 CONFDIR    = /etc
 CRONDIR    = /etc/cron.daily
-BINDIR     = $(PREFIX)/sbin
+BINDIR     = $(PREFIX)/bin
 DOCDIR     = $(PREFIX)/share/doc/$(PN)
 SCRIPTDIR  = $(PREFIX)/share/$(PN)/scripts
 SYSTEMDDIR = $(PREFIX)/lib/systemd/system

README.md

@@ -136,7 +136,7 @@ Retention policy:
 /etc/cron.daily/btrbk:
 
     #!/bin/sh
-    exec /usr/sbin/btrbk -q -c /etc/btrbk/btrbk-mylaptop.conf run
+    exec /usr/bin/btrbk -q -c /etc/btrbk/btrbk-mylaptop.conf run
 
 
   * This will create snapshots on a daily basis:
@@ -221,7 +221,7 @@ regular basis:
 /etc/cron.hourly/btrbk:
 
     #!/bin/sh
-    exec /usr/sbin/btrbk -q run
+    exec /usr/bin/btrbk -q run
 
 Note that you can run btrbk more than once an hour, e.g. by calling
 `sudo btrbk run` from the command line. With this setup, all those

doc/FAQ.md

@@ -28,7 +28,7 @@ How can I setup a debian pre-install hook?
 Create a file `/etc/apt/apt.conf.d/70btrbk`, e.g.:
 
     // create a btrfs snapshot before (un)installing packages
-    Dpkg::Pre-Invoke {"/usr/sbin/btrbk run /mnt/btr_pool/rootfs";};
+    Dpkg::Pre-Invoke {"/usr/bin/btrbk run /mnt/btr_pool/rootfs";};
 
 In order to make sure that the snapshots are always generated and
 nothing is deleted, add the btrbk command line options `--preserve