Adding changes that were made to the distribution branch that
should have gone into the exerpeimental branch in r2862.

Added a bunch of enhancements and fixed bugs involving data
missing fromthe image message headers.

Index: src/gscam.cpp
===================================================================
Added camera_name and camera_parameters_file globals for camera
info.

Moved ros init to the top of the main function.

Gets the gstreamer configuration either from environment variable
GSCAM_CONFIG or ROS param "~/gscam_config".

Gets the camera calibration parameters from the file located at ROS
param "~/camera_parameters_file", will look at
"../camera_settings.txt" by default.

A bunch of re-indenting for consistency.

Updated a lot of error fprintfs to ROS_ERROR calls.

Gets the TF frame_id from the ROS param "~/frame_id", can be over-
written by camera parameters.

Now sets the appropriate ROS timestap in the image message header.

Now sets the appropriate TF frame in the image message header.

Added more detailed info/error/warn messages.

Modified the warning / segfault avoidance added to experimental in
r2756. Instead of skipping the frame, it just copies only the
amount of data that it was received, and reports the warning each
time, instead of just once. In a large scale system with lots of
messages, a single warning might easily get lost in the noise.

Index: examples/webcam_parameters.txt
===================================================================
Added example camera parameters (uncalibrated) for a laptop webcam.

Index: examples/webcam.launch
===================================================================
Added a launchfile that makes use of the new rosparam options and
TF frame.

git-svn-id: http://brown-ros-pkg.googlecode.com/svn/trunk/experimental/gscam@2863 0d49d21e-669f-11de-873c-fb8c264d332a