dlsem (2.4)

* fixed the bug in lagPlot() for gamma lag shapes
* fixed the bug in causalEff() for multiple starting variables
* methods lagPlot() and causalEff() now return NULL instead of an error in case of inexisting path
* lag shape transformations are now visible to the user
* added the minimum gestation lag option in dlsem()
* added the gestation and the lead lags in the summary
* added the 'npar' method for class 'dlsem'
* added the vcovHAC() method for class 'lm' and 'dlsem'
* added the HAC estimate of standard errors in method dlsem()