Inconsistency with process' names

We have:

```r
library(simmer)

simmer() %>%
  add_generator("dummy", trajectory(), at(0)) %>%
  add_resource("dummy", schedule(c(8, 16, 24), c(3, 2, 1), period=24))
# Error: process 'dummy' already defined 
```
but
```r
simmer() %>%
  add_resource("dummy", schedule(c(8, 16, 24), c(3, 2, 1), period=24)) %>%
  add_generator("dummy", trajectory(), at(0))
# silent
```