Clashing g3_param_table g3_param ("haddock problem")

[lentinj]

As found in a haddock model, this makes a mess of initialising the parameters:

g3_to_tmb(list(
     g3_parameterized("K"),
     g3_parameterized("K", by_year = TRUE),
     g3a_time(1990, 1994) ))

It's a mistake in the model, but at very least we should handle it more gracefully.

• Give the K lookup a different name internally so both make sense?
• Error when compiling if there's a name clash?
• Let the param table override the first one, with some pre-transpile step?
• Implement g3_stock(... K = g3_parameterized("K", by_year = TRUE)), so these sorts of problems go away somewhat, as per #113