Generate plants in the map (so one can get seeds)

It is based on flowers but uses perlin to determine what plant to spawn (so the same plants are on the same chunks)
![screenshot_2321790051](https://f.cloud.github.com/assets/2786604/721404/ea8f29c6-dfe0-11e2-8e61-7791a7ffcead.png)
![screenshot_2321828303](https://f.cloud.github.com/assets/2786604/721405/eac044fc-dfe0-11e2-9d77-c04b7d2d8fd6.png)
![screenshot_2321844720](https://f.cloud.github.com/assets/2786604/721406/eac4d8c8-dfe0-11e2-9507-590af98c6611.png)
![screenshot_2321820405](https://f.cloud.github.com/assets/2786604/721407/ead953de-dfe0-11e2-9d10-00271cbc5dd5.png)
![screenshot_2321887116](https://f.cloud.github.com/assets/2786604/721408/eade439e-dfe0-11e2-95c9-80398f9cc1e7.png)
![screenshot_2321850984](https://f.cloud.github.com/assets/2786604/721409/eae5261e-dfe0-11e2-93e4-2a5271b7c918.png)