Atmos machinery sprite fixes

In this pull:
1. Passive gates had their on/off sprites flipped around in opposite directions, this is rectified.
2. 1-3 rogue pixels with an alpha of 10 have been removed from all the pumps and vents; they weren't visible in game but were annoying to me when mapping/spriting and had no reason to exist. (see pictures below)
3. Old sprites for the pumps removed because they were unused and UGLY AS SIN.

Before:
![image](https://f.cloud.github.com/assets/4343468/1172744/0c20a4c2-212a-11e3-8e87-33eac9a98cb1.png)

Now:
![image](https://f.cloud.github.com/assets/4343468/1172746/1aecab4a-212a-11e3-96f5-d34fda2ddbcd.png)