AIP #61 AdEx v5: Unified precision (8)

[elpiel]

https://github.com/AdExNetwork/aips/issues/61

Rust reference:

Issue: AmbireTech/adex-validator-stack-rust#384
PRs: AmbireTech/adex-validator-stack-rust#386

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Create a Unified Precision number (UnifiedNum) with precision of 8 that will be used for all calculations, except when we are creating the MerkleTree, where we need the actual precision of the token in order of the MerkleTree to be calculated properly.

• Token configuration of actual precision (in the configuration of the whitelisted token addresses)
• MerkleTree should use actual precision of the token (e.g. DAI - 18, USDT - 6, etc.)
• Use Unified Precision - UnifiedNum (including DB) & floor all the calculations
• Targeting rules DSL - use UnifiedNum instead of BigNum (see: V5 Targeting DSL - UnifiedNumber instead of BigNumber adex-protocol#67)