allow all entries with limit operator

[azimov]

Removes requirement for prior/post time and allows users to limit to 'all' events per subject should they satisfy prior/follow up time and calendar date requirements

[azimov]

Resolves #112

[codecov[bot]]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (c94c994) 98.54% compared to head (99c8526) 98.40%.

:exclamation: Current head 99c8526 differs from pull request most recent head 212fe1f. Consider uploading reports for the commit 212fe1f to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #117 +/- ## =========================================== - Coverage 98.54% 98.40% -0.15% =========================================== Files 12 12 Lines 1375 1378 +3 =========================================== + Hits 1355 1356 +1 - Misses 20 22 +2 ``` | [Files](https://app.codecov.io/gh/OHDSI/CohortGenerator/pull/117?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=OHDSI) | Coverage Δ | | |---|---|---| | [R/SubsetQueryBuilders.R](https://app.codecov.io/gh/OHDSI/CohortGenerator/pull/117?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=OHDSI#diff-Ui9TdWJzZXRRdWVyeUJ1aWxkZXJzLlI=) | `98.33% <100.00%> (+0.02%)` | :arrow_up: | | [R/Subsets.R](https://app.codecov.io/gh/OHDSI/CohortGenerator/pull/117?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=OHDSI#diff-Ui9TdWJzZXRzLlI=) | `96.98% <75.00%> (-0.59%)` | :arrow_down: |

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