Various fixes

- Fix for [Enable count rollup on any
field](https://github.com/afawcett/declarative-lookup-rollup-summaries/i
ssues/92)
- Fix for [Only one rollup per field working at a
time](https://github.com/afawcett/declarative-lookup-rollup-summaries/is
sues/63)
- Fix for [Multiple rollups on same field fail to
execute](https://github.com/afawcett/declarative-lookup-rollup-summaries
/issues/85)