Fix world ticking (soil hydration, crop growth, leaf decay). Fixes #734.

tickBlocksAndAmbiance() was broken in in build 283 by this merge:
https://github.com/MinecraftPortCentral/MCPC-Plus/commit/6f4d7cf6343d9ba260879f498f2ba3ae7a454fbb
the super.tickBlocksAndAmbiance() call was erroneously removed
during the merge, causing no block ticking to occur.

Re-add the missing call to fix farmland hydration, crop growth, leaf
decay, etc. Closes #734.
Restore vanilla default to aggregate-chunkticks

Spigot adds configurable chunk ticking for improved performance.
The default aggregate-chunkticks is well-suited for larger servers,
especially those which choose Spigot over vanilla CraftBukkit for
high-performance. However, on smaller servers this behavior may
be unexpected, leading to confusion when switching from vanilla Forge
to MCPC+.

This commit sets the default aggregate-chunkticks to 0, matching
vanilla behavior. If desired this option can be changed in bukkit.yml,
to Spigot's default of 4 or another value as desired. For more details
on configuring Spigot's features see this guide:
http://www.spigotmc.org/threads/spigot-configuration-guide-last-updated-3-24-2013.802/