TT#15750 Add our own npm registry cache to .npmrc

From now we have npmlazy cache available so let's use it wherever
possible. Exact dependencies versions must be controlled via
npm-shrinkwrap.json file otherwise we have no guarantee each time
package is build with the same dependencies tree.

Change-Id: I67653a8a4da1021b36f59474eb8f8112e37ae215

.npmrc

@@ -1 +1,2 @@
-save-prefix =
+save-prefix =
+registry = https://npm-registry.sipwise.com/