Fix markup in documentation for arcanist lint engine

Summary: Fixed wrong markup which was 1 space instead of 2

Test Plan: I couldn't test it as I don't know how to build documentation

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7587
Make ScriptAndRegexLinter available to ConfigurationDrivenLintEngine

See: <https://github.com/facebook/arcanist/pull/118>

Reviewed by: epriestley
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
Set limit for execution in C# linter

Summary: This sets the limit for future execution in the C# linter to 8.  See D7606 for more information.

Test Plan:
Ran

```
arc lint --everything --trace --never-apply-patches --output json
```

and saw it only run 8 commands at once.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7607
Improve exception raised when an event listener fails to load

Summary: See IRC. The failing class might not be the listener itself.

Test Plan:
  $ arc list
  ERROR: Failed to load event listener 'depr': Failed to load class or interface 'depr': the class or interface 'depr' is not defined in the library map for any loaded phutil library. If this symbol was recently added or moved, your library map may be out of date. You can rebuild the map by running 'arc liberate'. For more information, see: http://www.phabricator.com/docs/phabricator/article/libphutil_Libraries_User_Guide.html

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7616
ArcanistGitAPI: remove a bogus comment

See: <https://github.com/facebook/arcanist/commit/628de7d7a15cd7b5737515ec2831b3b4c3f601a5#commitcomment-4675543>

This comment is indecipherable even if it originally meant something.

Reviewed by: epriestley
ArcanistGitAPI: document a git ls-files bug

When a submodule is ignored (ignore=all in .gitconfig),

  $ git ls-files -m

fails to exclude the submodule from the listing. Other commands like

  $ git diff-index --name-only HEAD

exclude it just fine.

See: <https://github.com/facebook/arcanist/pull/120>

Reviewed by: epriestley
ArcanistGitAPI: replace 'ls-files -m' with diff-files

As documented,

  $ git ls-files -m

fails to exclude ignored submodules. Replace it with an equivalent:

  $ git diff-files --name-only

which does not suffer from this defect.

See: <https://github.com/facebook/arcanist/pull/121>

Reviewed by: epriestley
Merge branch 'master' of http://github.com/facebook/arcanist