refactor: GlossaryTextArea: action with lambda

[miurahr]

This refactor GlossaryTextArea class. The proposed change improve readability of code and help debug to avoid anonymous action listener class.

Pull request type

• Other (describe below) refactor

Which ticket is resolved?

What does this PR change?

• Define utility class to create menu item in GlossaryTextArea
• Use these class to define Glossary screen pop-up menus.
• define utility openWritableGlossaryFile in ProjectUICommand class

Other information

dev-ML discussion https://sourceforge.net/p/omegat/mailman/omegat-development/thread/2ab347a7-536f-4e3b-bac6-a8856c00112d%40northside.tokyo/#msg58776083

Suggest that we can use Java standard Actons interface for menu items