Land Generation layers/JSON settings

There are now two types of land generation layers, Simple and Iterative.
The sole major diferance between the two types of land generation layers
is that iterative land generation uses different seeds for each
itteration while the simple uses only one seed. Simple uses slightly
less memory as such, though I doubt if it would show any noticiable
performance improvements.

The chunk provider now has basic support for configeration settings. It
uses json as the storage format in the settings string. This should
allow for easy adding of properties as needed, without having to rewrite
a parser, at the cost of slightly larger strings due to the nested and
slightly more verbose nature.