Setting names are no longer strings

Now they use the TCSetting interface. In the future, the setting read
and write logic could be handled by TCSetting instead of ConfigFile.
ConfigFile would then call the method setting.read(String value) and
setting.toString() or something.
Improve some comments in the WorldConfig

Also changed a few titles to be more consistent between the WorldConfig
and BiomeConfig.
Remove writeNewLine() in configs

Now a new line is included in writeValue(..). This change removes a lot
of boilerplate code. It also makes it harder to write too few or too
many blank lines.

Sometimes it is still necessary to print out a blank line, for example
in a long comment. You can still use writeComment("") for this - when
the comment is blank, the # at the beginning of the line won't be
printed. (This behaviour of writeComment("") existed before.)