Implemented password hashing. Added and improved tests.

src/test/json/strawboss.config.json

@@ -1,10 +1,11 @@
 {
   "artifactsRepo": "artifacts",
+  "authSecret": "change me",
   "users": [
     { "name": "bob@builder.com", "hashedPwd": "testvalue" },
     { "name": "sam@sousa.com", "hashedPwd": "testvalue" }
   ],
-  "authSecret": "change me",
+  "pwdCost": 11,
   "projects": [
     { "name": "test-project-1",
       "repo": "/non-existent/dir",