Include English locale in base.

This change causes the "base" element to install and generate English
locales, thereby mitigating a lot of build noise (at least for
English speaking users). Also included is a note in the element's
README.md about what users in other locales should do.

Change-Id: I053c7e0254a0a0d7dde081f7cc72204a12aa8ef4

elements/base/README.md

@@ -0,0 +1,12 @@
+This is the base element.
+
+Almost all users will want to include this in their disk image build,
+as it includes a lot of useful functionality.
+
+Notes:
+
+ * If you are getting warnings during the build about your locale
+   being missing, consider installing/generating the relevant locale.
+   This may be as simple as having language-pack-XX installed in the
+   pre-install stage
+

elements/base/pre-install.d/00-baseline-tools

@@ -4,5 +4,5 @@
 set -e
 
 apt-get -y update
-apt-get -y install python-software-properties
+apt-get -y install python-software-properties language-pack-en
 add-apt-repository -y ppa:tripleo/demo