First batch of cros-disk changes

A couple of things in this CL.

1. Adds an upstart script that runs the daemon as cros-disks.
2. Adds some functions to the d-bus API.
3. Adds support for watching udev for changes.
4. Adds a DiskManager class for processing disk changes.
5. Adds a Disk class to store the properties that we care about.
6. Some Makefile changes to fix NDEBUG and gflags issues.

Change-Id: I92f7d9199b71aa0150ad82cabe36c5396a4603c8

TEST=Ran the autotest and manually tested that I was getting udev changes on a cr-48.

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12 files changed