Add .gitignore and .gitreview files

Add the .gitignore and .gitreview files to the asterisk repo.

NB:  You can add local ignores to the .git/info/exclude file
without having to do a commit.

Common ignore patterns are in the top-level .gitignore file.
Subdirectory-specific ignore patterns are in their own .gitignore
files.

Change-Id: I4c8af3b8e3739957db545f7368ac53f38e99f696
Tested-by: George Joseph