Configfile include

[thelusiv]

I checked in some changes which include more error checking. Some thoughts:

• came up with some error cases for sections and subsections but they turned out to be used in the game in different ways. they are commented out (config.cpp:186-213). i think that some of these things should be at least warnings, since users probably won't usually intend to duplicate a section, or other things like that.
  
• it would be a pain to get loggers in CONFIG, since CONFIG objects are created in many different places (and owner objects don't always have loggers either), so i am going to work on that later (or maybe try to write a script to do it)
  
• on sections, subsections, etc.: there is a way to find the children of a section (childrens' names are stored on config.cpp:201), but not to find a given section's parents. why store this hierarchy information, is it used anywhere?
  
• would it make any sense to make SECTION a custom class instead of just a map<string, string>? this would make it easier to facilitate things like finding parents (and siblings, and root nodes, etc.) to support a proper hierarchy. if this was implemented, it wouldn't be difficult to refer to other values stored in the file by their names. (would that be useful?)