DocSearcher 4.0.0 released

This is a major release after a long time.
This release contains three important things and many other changes.

• Java 11 is now the minimum required Java version
• working directory was changed to .docsearcher2 (no configuration will be adopted - this release starts with default)
• working directory under windows was moved to user home directory

Please use the feedback in DocSearcher to help us with the development of DocSearcher.