WIP Upgrading to Nim 0.19. Getting docker pieces compiling.

* Addressing breaking changes in migration from Nim 0.18 to 0.19.
* Finishing the initial pass at the refactor required to include
  docker-based builds.
* Regaining confidence in the existing functionality by getting all
  tests passing again after docker introduction (still need new tests to
  cover new docker functionality).

src/test/nim/functional/tserver.nim

@@ -50,7 +50,7 @@ suite "strawboss server":
       @["serve", "-c", tempCfgPath], loadEnv(), {poUsePath})
 
     # give the server time to spin up
-    sleep(100)
+    sleep(200)
 
   teardown:
     discard newAsyncHttpClient().post(apiBase & "/service/debug/stop")
@@ -60,7 +60,7 @@ suite "strawboss server":
       removeFile(tempCfgPath)
 
     # give the server time to spin down but kill it after that
-    sleep(100)
+    sleep(200)
     if serverProcess.running: kill(serverProcess)
 
   test "handle missing project configuration":