Set simulation projection of age structure population through space and time

[AngeliaMiller]

For both scup and summer flounder based on results from issue #2 and issue #3 , respectively

Expected output: R object that contains spatial distribution of age-structure through time on the new NE US grid instead of the SimSurvey default grid

[AngeliaMiller]

Simulation of summer flounder abundance and distribution over survey area grid, found here

• [x] simulates abundance based on stock assessment data
• [x] simulates distribution based on model fit parameters from sdmtmb (may need to adjust based on historical data?)
• [x] simulates a survey over the distribution
• [x] calculates the stratified mean abundance index from simulated survey data
• [x] compares to true stratified mean abundance index

revisit to adjust to capture actual population? - simulated abundance index is orders of magnitude larger than observed index.

[AngeliaMiller]

summer flounder projection found in 02-append-sumflounder-dist.Rmd through commit 6c8138e.