Beach, Orchard, Mud metatile alignments, and reducing symbol size for allotments

Summary:

Providing a fix for #299 - this changes the symbols for beach and orchard,
as well as mud.png exactly the same style, that would clear all 10px cases in #937
allotments.png just reduced in size without visual change.

Details:

For Beach, Orchard, Mud:
To maintain pixel-crispiness while bending to the Power of Two the density of the pebbles
has been reduced from 4+1 pixels to 7+1 pixels. 

This follows the opinion in fixing the allotments in #770, where the wider style was accepted as
adding more clarity to the map. 

New tiles:
![beachtile_687526](https://cloud.githubusercontent.com/assets/8266355/4293648/4c92cf50-3dd8-11e4-8633-fcff80d607b3.png)
![orchardtile_21538](https://cloud.githubusercontent.com/assets/8266355/4293649/4c973784-3dd8-11e4-8e73-a6c5f7e59a55.png)

edit: Adding 3+1 style for direct comparison, from discussion below:
![beachtile_4x4_687527](https://cloud.githubusercontent.com/assets/8266355/4294659/d98cff9e-3de1-11e4-86ce-33acbe195058.png)

Examples of current metatile artefacts:
http://www.openstreetmap.org/#map=18/52.37324/12.87641

Resolves #299.