drc dependencies

Using the cran version drc will result in warnings below:


```
#> Warning in (tquan * sqrt(varVal + sumObjRV)) * c(-1, 1): Recycling array of length 1 in array-vector arithmetic is deprecated.
#>   Use c() or as.vector() instead.

```

Currently is built with github version of drc, which requries drcData. This needs to be resolved for validation purpose. 