Support for changing capturing and streaming parameters in ROS

[ramsafin]

This issue is closely related to #5 and #6 where parameters of video capture can be changed in runtime. Those parameters include v4l2 controls (e.g. gain, saturation, whitebalance, etc.), frame resolution and frame rate (streaming process needs to be reloaded), and others.

Parameters could be changed either via service calls or dynamic reconfigure.