README: unify command line instructions

* Unify the convention for which `#` and `$` indicate whether the command
  requires super-user permission

* Break off `apt install` instructions on multiple lines, and sort
  package names.

Author: dacav

README

@@ -22,31 +22,31 @@ list is available below.
 
 [source, console]
 ----
-$ sudo apt install libpam-u2f pamu2fcfg
+# apt install libpam-u2f pamu2fcfg
 ----
 
 Additionally, Yubico maintains a PPA with up-to-date versions of pam-u2f.
 
 [source, console]
 ----
-$ sudo apt install software-properties-common
-$ sudo apt-add-repository ppa:yubico/stable
-$ sudo apt update
-$ sudo apt install libpam-u2f pamu2fcfg
+# apt install software-properties-common
+# apt-add-repository ppa:yubico/stable
+# apt update
+# apt install libpam-u2f pamu2fcfg
 ----
 
 === Fedora
 
 [source, console]
 ----
-$ sudo dnf install pam-u2f pamu2fcfg
+# dnf install pam-u2f pamu2fcfg
 ----
 
 === macOS
 
 [source, console]
 ----
-$ brew install pam-u2f
+brew install pam-u2f
 ----
 
 [[building]]
@@ -62,16 +62,23 @@ installed using
 
 [source, console]
 ----
-# apt install --no-install-recommends autoconf automake libtool pkg-config \
-    libfido2-dev libpam-dev libssl-dev
+# apt install --no-install-recommends \
+    autoconf \
+    automake \
+    libfido2-dev \
+    libpam-dev \
+    libssl-dev \
+    libtool \
+    pkg-config \
+;
 ----
 
 If you downloaded a tarball, build it as follows.
 
 [source, console]
 ----
-$ ./configure
-$ make
+./configure
+make
 ----
 
 Once the module is built, copy the file `pam_u2f.so` to the correct
@@ -102,18 +109,35 @@ $ cd pam-u2f
 the necessary dependencies can be installed using
 
 [source, console]
-----
-# apt install --no-install-recommends autoconf automake libtool \
-    pkg-config libfido2-dev libpam-dev libssl-dev asciidoc xsltproc \
-    libxml2-utils docbook-xml
+----sh
+# apt install --no-install-recommends
+    asciidoc \
+    autoconf \
+    automake \
+    docbook-xml \
+    libfido2-dev \
+    libpam-dev \
+    libssl-dev \
+    libtool \
+    libxml2-utils \
+    pkg-config \
+    xsltproc \
+;
 ----
 
 On Fedora, the necessary dependencies can be installed using
 
 [source, console]
 ----
-# dnf -y install autoconf automake libtool libfido2-devel pam-devel \
-    openssl-devel asciidoc
+# dnf -y install \
+    asciidoc \
+    autoconf \
+    automake \
+    libfido2-devel \
+    libtool \
+    openssl-devel \
+    pam-devel \
+;
 ----
 
 Generate the build system using: