Upgrade C# linter to support linting multiple files at a time

Summary:
This upgrades cslint to support linting multiple files at a time. As this required a backwards-incompatible to cslint, I've added a SUPPORTED_VERSION constant which can be used to detect these kinds of breaking changes in the future (and prompt users to upgrade the cslint they have in their repository).

The reason for this upgrade is mainly around running arc lint --everything, where there are significant performance benefits gained when bulk linting lots of files per command execution.

Test Plan: Upgraded cslint in the Tychaia repository and ran arc lint --everything --trace. Saw a substantially less number of executions happening for linting and all of the results came through as expected.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran, waynea

Differential Revision: https://secure.phabricator.com/D7599