Catch missing RO2 species error when prepping

[kilicomu]

Adds an exception where an RO2 species is encountered in the RO2 sum of the mechanism file but isn't encountered in the mechanism species list.

We shouldn't get to a point where there is an RO2 species in mechanism.ro2 that isn't in the full species list in the mechanism, so I think the user needs to correct their mechanism before building and running the model, as opposed to a warning being shown and them being allowed to erroneously continue.

I had a look at adding some error handling to the ro2Sum function in outputFunctions.f90 - it is a pure function which disallows error stop. I think there would be a bit too much unpicking to make that error handling neat, so I avoided it.

Let me know what you think - happy to make changes as requested.

Closes #453

[codecov[bot]]

Codecov Report

Merging #457 (283e1b6) into master (aeffeb2) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #457   +/-   ##
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  Coverage   65.51%   65.51%           
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  Files          17       17           
  Lines        2047     2047           
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  Hits         1341     1341           
  Misses        706      706           

Flag	Coverage Δ
build	52.23% <ø> (ø)
tests	82.81% <ø> (ø)
unittests	31.61% <ø> (ø)

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