fix seed placement and add translation support and update env and fix sword

basically everything from other fork and my own fix

https://github.com/PilzAdam/farming_plus/issues/10: seed can now only be place on group:soil, code from farming mod
https://github.com/PilzAdam/farming_plus/pull/4: note from http://dev.minetest.net/EnvRef
```
Important Note: Since 0.4.7, minetest.env is deprecated. This feature won't be dropped soon to not break compatibility with older mods, but will be removed in a future version.
```
https://github.com/PilzAdam/farming_plus/pull/5: apple drop too so why not?
https://github.com/PilzAdam/farming_plus/issues/9: now all sword works