Added global page segmentation mode configuration to preferences

• Added Visual Studio code and Eclipse project files to .gitignore
• Added support for images with 4 byte RGBA color components (this was a silent error)
• Updated source compatibility from Java 6 to Java 7 and added alternate Java EE API specifically for Java 11

For users that need to configure a different PSM in the underlying tesseract engine, this allows them to persist and apply the configuration on the fly.

Notes:

• This is a destructive action; if you are performing box editing this will cause the RecognitionWorker to execute again which will re-render all page model components. This behavior could be improved by allowing the user to confirm before applying changes, removing the behavior altogether, or perhaps moving the preference into relevant controls pane (common pane?).
• Having a per-image configuration may be desirable
• More on Java 11 via StackOverflow: https://stackoverflow.com/questions/52502189/java-11-package-javax-xml-bind-does-not-exist