(QENG-2208) Move Sinatra Helpers to own file

This moves the inline Helpers contained in V1.rb to their own file:
helpers.rb. In making this change, any API.settings call was removed
from the helper method itself and passed through from V1.

This also adds tests for hostname shortener and validate date string.

lib/vmpooler/api.rb

@@ -30,7 +30,7 @@ module Vmpooler
     use Vmpooler::Dashboard
 
     # Load API components
-    %w( dashboard reroute v1 ).each do |lib|
+    %w( helpers dashboard reroute v1 ).each do |lib|
       begin
         require "api/#{lib}"
       rescue LoadError