Clang-tidy: added --disable-checks, --list-checks options.

Summary:
Allow disabling checks by regex. By default, disable alpha.* checks,
that are not particularly good tested (e.g. IdempotentOperationChecker, see
http://llvm-reviews.chandlerc.com/D2427).

Fixed a bug, that would disable all analyzer checks, when using a regex more
strict, than 'clang-analyzer-', for example --checks='clang-analyzer-deadcode-'.

Added --list-checks to list all enabled checks. This is useful to test specific
values in --checks/--disable-checks.

Reviewers: djasper, klimek

Reviewed By: klimek

CC: cfe-commits, klimek

Differential Revision: http://llvm-reviews.chandlerc.com/D2444

git-svn-id: http://llvm.org/svn/llvm-project/clang-tools-extra/trunk@197717 91177308-0d34-0410-b5e6-96231b3b80d8