Pools; new option added for auto-sequenced Pool codes

Pool codes can now be auto-sequenced.

The next Pool code is defined under Tools, Global Settings, Accounts group, Pools page.

If the Next Pool code is defined and the Pool code is left blank, when saved the Pool's code will automatically be set to the next code, and the Next Pool code will be incremented and updated under Global Settings.

In addition, Pools can now be added with no Accounts attached to them.