Add a 'remove ruleset' button on preference page

[marvinvo]

Description

This changes will add a "remove selected ruleset" button to the preference page.

Fixes #464

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A
• Test B

Test Configuration:

• Eclipse Version:
• Java Version:
• OS:

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
  • eclipse preference recorder is listening to changes on rulesets and will notify the developer on saved changes
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes