Extended simulation example

[mdevans21]

Add excel example simulations using full frequency and severity modeling with a copula for corrlations between loss types:

1. Simulate attritional losses using capped log-normal
2. Simulate large losses using frequency (negative binomial) and severity (log-normal)
3. Simulate cat losses using input EP curve

Correlate loss types with student-t copula. Use high correlation ~0.7 between attritional and large frequency, low correlation between large severity ~0.1, low correlation with cat ~0.1.