Feature/try mode

[MarcDahlem]

Replaced the very limited current test adapter, with a try-mode adapter.

Changes/Improvements:

• The new try-mode adapter tracks the created dummy orders, and fill them if the corresponding limit price is reached
• Instead of sending all public api calls to bitstamp, the adapter to be used can be configured
• All starting balances and currencies for the try-mode can be configured

[MarcDahlem]

The PR should be ready?

[gazbert]

Finally started getting this back to master - sorry @MarcDahlem , it's been a hectic couple of years! :-)

A few minor Checkstyle issues + README / Javadocs / config docs updates required...

It's low risk and does not affect existing functionality, so I'll probably merge to master and then make the fixes off of that.

1.4.0 release will then follow.

[gazbert]

Merging to master. Will fix the Checktyle issues there. And update the docs for the new feature etc.