em.control: Create a control structure for running EM algorithms
In chaudhary-amit/acblm: Two step estimation of three sided heterogeniety

Create a control structure for running EM algorithms

1	em.control(ctrl = NULL, ...)

`nplot`	how often to plot wages of comparaison to model0
`ncat`	how often to log information
`maxiter`	maximum number of iterations
`model_var`	whether to allow for flexible variance (default is TRUE)
`est_Amb`	TBD
`cstr_type`	defines the type of constraints on the means for estimation
`cstr_val`	TBD
`tol`	tolerance for stopping the EM
`tau`	posterior likelihood to use instead of computing them using initial parameters
`model0`	model to compare estimation to when plotting
`presp=1e-9`	TBD
`rel_weight`	setting a particular weight for stayers versus movers (default is 1)
`est_rho`	vector of TRUE/FALSE that states which rho should be estimated
`rho_in_diff`	whether to estimate rho in level of in differences
`dprior`	Dirichlet prior for proportions (default 1.01)
`nfirms_to_update=10,`	number firms to update in probabilistic approach
`proba_include`	what terms to include in the liklihood for probabilistic approach (default to = c(1,1,1,1))
`check_lik`	whether to check the likelihood at each updating parameter
`stochastic`	whether to use stochastic EM instead of straight EM
`fixb`	when TRUE, imposes fixed interactions in different time periods
`fixm`	when TRUE, levels are not updated, only variances and proportions
`deps=1e-50`	TBD
`file_backup_prefix`	TBD
`sd_floor=`	floor imposed on all standard deviations (default is 1e-10)
`posterior_reg`	term added to posterior probablities (this is to deal with numerical issues, default is 1e-9)
`textapp`	text to show in logging
`sdata_subsample`	share of the stayers to use in estimation
`sdata_subredraw`	whether to redraw the subsample of stayers
`vdec_sim_size`	size to use in simulation
`stayer_weight`	weight attributed to stayers in joint estimation
`est_rep=`	number of starting values for EM
`est_nbest`	number of best starting values to select from using connectedness