Throw errors on an incorrect release

[Enchufa2]

Throw an error in these cases:

• Not previously seized:

t <- create_trajectory() %>% 
  release("dummy", 1)

env <- simmer() %>% 
  add_resource("dummy", 1) %>% 
  add_generator("asdf", t, at(0)) %>%
  run()

• Incorrect amount:

t <- create_trajectory() %>% 
  seize("dummy", 1) %>%
  release("dummy", 2)

env <- simmer() %>% 
  add_resource("dummy", 1) %>% 
  add_generator("asdf", t, at(0)) %>%
  run()