Add capture recapture lab

Note this is nowhere near ready… Still half sweave, but I wanted to get it in the tree.
Conversion from sweave to knitr completed.

Started switch from binomial to hypergeometric (and correct)
Correction to simulation code.
Split capture-recapture lab into multiple parts and update each.
Parts 1-3 are included in this commit. Part 4 (Bayes) will be added later.
Major updates to the text and organization.
Add link to capture-recapture lab from main page.