Resolve "[Docker] Install some system utilities in base image"

Closes #595 (closed)

CHANGELOG.rst

@@ -35,6 +35,7 @@ Changed
   * Name collisions are resolved by prefixing with the app label
   * Apps can extend SHELL_PLUS_APP_PREFIXES and SHELL_PLUS_DONT_LOAD
 
+* [Docker] Base image now contains curl, grep, less, sed, and pspg
 * Views raising a 404 error can now customise the message that is displayed on the error page
 * OpenID Connect is enabled by default now, without RSA support