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/testutil.nim

@@ -26,7 +26,7 @@ proc waitForBuild*(client: HttpClient, apiBase, projectName, runId: string,
     #echo "Checking (" & $curElapsed & " has passed)."
 
     if curElapsed > toFloat(timeout):
-      raise newException(SystemError, "Timeout exceeded waiting for build.")
+      raise newException(Exception, "Timeout exceeded waiting for build.")
 
     let resp = client.get(apiBase & "/project/" & projectName & "/run/" & runId)