Merge in changes from 1.8
Removed tag 1.8
Removed tag 1.8.0
Merge in correction from 1.8
Update docs.

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branch : 1.9
Update roadmap

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branch : 1.9
Ensure memory is freed up. This causes problems with some formulae.

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branch : 1.8
Fix failing test with formulae by skipping. Formulae and values are handled within cells.

--HG--
branch : 1.8
Merge memory improvements from 1.8
Merge

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branch : 1.9