Add checkstyle prebuilt jar and move checkstyle.py and related files

- This adds Checkstyle 7.4-SNAPSHOT
  Taken from internal builder:
    https://android-build.googleplex.com/builds/branch-dashboard/ub-checkstyle-master?build_id=3575892
  Built from external/checkstyle 4f80bd71c5c6647112ae74163e8548e2f44e7e98
- This moves checkstyle.py and related files from
  platform/development to this repo.

Bug: 33078621
Test: Ran checkstyle.py on some test java files.
Change-Id: I91b196fb87ad01d171bf4250ce5a2101d6890a59
diff --git a/README b/README
new file mode 100644
index 0000000..d147f8b
--- /dev/null
+++ b/README
@@ -0,0 +1,28 @@
+Description:
+Checkstyle is used by developers to validate Java code style before running repo upload.
+
+It can be invoked in two ways.
+1. To check style of entire specific files:
+checkstyle.py -f FILE [FILE ...]
+2. To check style of the lines modified in the latest commit:
+checkstyle.py
+
+Projects used:
+* Name: Checkstyle
+  Description: Checkstyle is a development tool to help programmers write Java code that
+               adheres to a coding standard.
+  URL: http://checkstyle.sourceforge.net/
+  Version: 7.4-SNAPSHOT
+  License: LGPL 2.1
+  License File: LICENSE
+  Source git repo: https://android.googlesource.com/platform/external/checkstyle
+
+* Name: Git-Lint
+  Description: Git-lint is a tool to run lint checks on only files changed in
+               the latest commit.
+  URL: https://github.com/sk-/git-lint/
+  Version: 0.0.8
+  License: Apache 2.0
+  License File: gitlint/LICENSE
+  Local Modifications:
+  - Downloaded gitlint/git.py and git/utils.py files individually.