Add -exec-arguments command

Summary:
This patch adds -exec-arguments command for lldb-mi. -exec-arguments command allows to specify arguments for executable file in MI mode. Also it contains tests for that command.

Btw, new added files was formatted by clang-format.

Reviewers: abidh, zturner, clayborg

Reviewed By: clayborg

Subscribers: zturner, emaste, clayborg, jingham, lldb-commits

Differential Revision: http://reviews.llvm.org/D6965

llvm-svn: 229110