Ensure that package managers clean up

Every package manager should clean up after themselves in order to keep
docker layers neat and tiny:

apt (Debian/Ubuntu package manager):

 - unneeded dependencies are cleared (autoremove)
 - caches are cleaned (clean)
 - package lists are deleted

yum (CentOS package manager),
zypper (OpenSuse package manager)

 - should clear caches after installing dependencies

pip (Python package manager),
apk (Alpine package manager)

 - should use no cache for installing dependencies

scripts/install-essentials

@@ -16,8 +16,6 @@ apt-get install -y \
 	libkrb5-dev postgresql-client mysql-client unzip \
 	libre2-dev gettext \
 
-apt-get clean -yqq
-
 # Set UTF-8
 # http://stackoverflow.com/a/3182519/2137281
 LOC=$'LC_ALL=en_US.UTF-8\nLANG=en_US.UTF-8'
@@ -28,4 +26,6 @@ locale-gen
 dpkg-reconfigure locales -f noninteractive -p critical
 locale -a
 
+apt-get autoremove -yq
+apt-get clean -yqq
 rm -rf /var/lib/apt/lists/*