[PEAK] Wiki changes

[John Landahl]

I've made some fairly extensive changes to the main Wiki page, which included 
moving existing text to separate pages and the addition of a "PEAK at a 
Glance" diagram.  The diagram shows the primary components of PEAK as stacked 
boxes, color coded to give a rough indication of stability.  Let me know if 
there are any inaccuracies, if you can think of a better classification or 
color scheme, if you think anything needs to be added (e.g. peak.tools), etc.

I've renamed the main title bar to "Introduction to PEAK" (from "PEAK 
Developers' Center", which is already indicated in the main navbar) and added 
two subsections, "Getting Started" and "Tutorials".  The "Getting Started" 
section replaces the previous main text with short narratives on the primary 
modules, which now have (or will have) their own separate pages.  The 
existing text was moved to these separate pages, and FEATURES.txt was used to 
fill in some of the gaps.  FEATURES.txt was also used for some of the 
mini-narratives.

The Tutorials subsection highlights the IntroToPeak page and enumerates the 
other user-contributed tutorials.  The old "User Contributions" section has 
been renamed "Miscellaneous" for now, with it's remaining contents listed as 
"to be categorized".  Finally, the stock FrontPage introductory text now has 
its own section called "Using the Wiki".

There's still a lot of work to be done in fleshing out all the new pages, but 
hopefully what's been done so far is a small step forward.