Added initial lro_wac driver

[AustinSanders]

Includes initial lro_wac driver.

This PR should not be merged until more work is completed on the ephemeris stop time. In its current state, the stop time from the ale output does not match that of the isis output.

[jessemapel]

Related to #446

[jessemapel]

You are likely seeing timing differences because of a few complications in how push frames work vs linescanners.

First, with linescanners, to get the end time we count the number of lines. For pushframes, we want to instead count the number of frames.

Second, we have a meaningful difference between the exposure duration and the inter_frame_delay. The exposure duration is how long each frame is exposed for. The inter frame delay is the time between exposures. For line scan sensors these values are usually very close. For push framers, though, the exposure duration is often significantly shorter than the inter frame delay.

So here's the different end_time equations:

line scan

end_time = start_time + exposure_duration * num_lines

push frame

end_time = start_time + inter_frame_delay * (num_frames - 1) + exposure_duration

Note that we do (num_frames - 1) because we are counting the delay between frames, I always think of fence posts vs fence rails for these situations. Also, we add the exposure_duration to account for the time it takes for the final frame to be exposed.

[AustinSanders]

Closing in favor of #447