Split testing into unit and functional tests.

* Split the `test` nimble task into `unittest` and `functest`, with
  corresponding test directories and test runners.
* Added documentation in README regarding building and testing StrawBoss.
* Created a small, simple test project for use in the functional tests.
* Added a `keepEnv` template in the server unit test code to make it easy to
  preserve the working environment for a single unit test to invistigate
  failures manually.

src/main/nim/strawbosspkg/configuration.nim

@@ -74,8 +74,17 @@ proc findProject*(cfg: StrawBossConfig, projectName: string): ProjectDef =
     raise newException(KeyError, "multiple projects named " & projectName)
   else: result = candidates[0]
 
-# internal utils
+proc setProject*(cfg: var StrawBossConfig, projectName: string, newDef: ProjectDef): void =
+  var found = false
+  for idx in 0..<cfg.projects.len:
+    if cfg.projects[idx].name == projectName:
+      cfg.projects[idx] = newDef
+      found = true
+      break
 
+  if not found: cfg.projects.add(newDef)
+
+# internal utils
 let nullNode = newJNull()
 proc getIfExists(n: JsonNode, key: string): JsonNode =
   # convenience method to get a key from a JObject or return null