Added buttons for new enhanced UI community contribution, various minor fixes and enhancements

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https://github.com/afawcett/declarative-lookup-rollup-summaries/issues/2
3
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https://github.com/afawcett/declarative-lookup-rollup-summaries/issues/2
2
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https://github.com/afawcett/declarative-lookup-rollup-summaries/issues/2
1
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https://github.com/afawcett/declarative-lookup-rollup-summaries/issues/1
6
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https://github.com/afawcett/declarative-lookup-rollup-summaries/issues/5
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https://github.com/afawcett/declarative-lookup-rollup-summaries/pull/15