Add more tree generators

*Edited by turt2live*

**Related Links:**
- Ticket: #76 

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It adds the following trees:
 - Acacia
 - Dark Oak
 - Swamp tree
 - Jungle bush
 - Big jungle tree
 - Tall redwood tree (those who have just a few leaves)
 - Mega redwood tree

#### Test Plugin:
- jar: https://drive.google.com/file/d/0B0gnjB7PN1h3d2YxM25MWVZ6ZmM/view?usp=sharing
- source available here: https://gist.github.com/jimmikaelkael/3d3448223c64870bbecd

![Acacia](http://s17.postimg.org/mhzha207z/2014_10_28_18_14_29.png)

![Dark Oak](http://s30.postimg.org/9q9k1prw1/2014_10_25_21_04_33.png)

![Swamp tree](http://s22.postimg.org/lfc444y8x/2014_10_28_18_22_41.png)

![Jungle tree](http://s3.postimg.org/rhags5itf/2014_10_28_18_02_06.png)

![Tall redwood](http://s24.postimg.org/l4e1o23bp/2014_10_28_18_26_44.png)

![Mega redwood tree](http://s29.postimg.org/ywp0if3dz/2014_10_28_18_04_19.png)