Resource, DomainTool: support per slice price configuration in several supplies.

also update tests to check if a duplicated supply will not cause doubled price.
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Status Job ID Name Coverage
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failed ERP5.CodingStyleTest-Master

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failed ERP5.PerformanceTest-Master

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failed ERP5.UnitTest-Master

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failed ERP5.UnitTest-Master.Medusa

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python3

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python2

passed SlapOS.Eggs.UnitTest-Master.Python3

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