sh: Add internet-check base script

Added script to sh base package to allow checking for internet
connectivity. Checks both through system virtual filesystem and, as a
fallback, through pinging google dns.

Added a simple readme to sh module.

sh/README.md

@@ -0,0 +1,20 @@
+# sh
+
+The bare minimum terminal configuration for a working system.
+Contains:
+
+* an XDG compliant home directory setup
+* several basic environment variables
+* simple aliases
+* an optional fzf default setup
+* X autostart
+
+While other modules are largely optional, 
+this module is the only one strictly necessary for the system to really work at all.
+
+Additionally contains two scripts on which some other modules build:
+
+* a simple script to detect if applications exist
+  (and optionally warn the user if they don't)
+* and a script to check if internet connectivity exists
+