Added all about the new config file format. Needs checking for accuracy.
Also need to update the faq and other sections of the docs now that the
options page is gone.
Added faq entry about exorbitant memory usage
updated features section on the main page
Added a "what overviewer is not" section on main page
put new rendermodes on the options page
re-worded some things under the custom rendermodes section
also added a link to the faq under help on the index page
also clarified the faq entry about adding new features or changing
texture packs
also fixed a typo
