If you have a development branch for a major project that
will receive gerrit reviews it'll probably be named something
like "development/16/newproject".  That will necessitate setting
"defaultbranch=development/16/newproject" in .gitreview.  The
make_version script uses that variable to construct the asterisk
version however, which results in versions like
"GIT-development/16/newproject-ee582a8c7b" which is probably not
what you want.  Worse, since the download_externals script uses
make_version to construct the URL to download the binary codecs
or DPMA.  Since it's expecting a simple numeric version, the
downloads will fail.

To get this to work, a new variable "basebranch" has been added
to .gitreview and make_version has been updated to use that instead
of defaultversion:

.gitreview:
defaultbranch=development/16/myproject
basebranch=16

Now git-review will send the reviews to the proper branch
(development/16/myproject) but the version will still be
constructed using the simple branch number (16).

If "basebranch" is missing from .gitreview, make_version will
fall back to using "defaultbranch".

Change-Id: I2941a3b21e668febeb6cfbc1a7bb51a67726fcc4

Change-Id: Ib2c42fc2d46563e2fbadbd5513cb029b4042791e

Change-Id: I459dc320a8c9452a01eed6f403d786741587c890

Although the default value of defaultbranch is master I'm adding it
anyways.  This way when new major branches are being created the value
can be updated instead of having to remember the name of the key.

Change-Id: I3db009217c5ae399fb84bee95076f4dbb7fa52d2

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: I842a1588ff27d8a0189f12d597f0a7af033d6c69
Tested-by: George Joseph