Replace Position criteria with Above/Below criteria

[edouardpoitras]

Position criteria is a bit more convoluted than necessary. Replace with a Above and Below criteria.
Instead of Position(technical_indicator1, 'below', technical_indicator2), we should have Below(technial_indicator1, technical_indicator2).
Same thing for the Above criteria.

[edouardpoitras]

This change has been implemented in the develop branch and will be available on the next minor release.