Simplify and Refactor RAM Market Equations

[zorba80]

Change Description

1. Simplified RAM market Bancor calculations by using direct conversion from SYS to RAM and vice-versa instead of the indirect conversion: SYS -> RAMCORE-> RAM and RAM->RAMCORE->SYS.
2. Changed the exchange_state functions convert_to_exchange and convert_from_exchange to reflect directly the equations in Bancor white paper.
3. Updated REX to use get_bancor_output from exchange_state in order to avoid code repetition.
4. Verified that the indirect conversion using the old functions and the indirect conversion using the new functions both give the same effective direct conversion equation introduced in this PR. The old convert_to_exchange and convert_from_exchange functions when used individually were not an accurate implementation of the Bancor equations in the white paper, but when used together, the variations cancelled and the overall output is the same. We verified that both mathematically and in unit tests.

Deployment Changes

• Deployment Changes

API Changes

• API Changes

Documentation Additions

• Documentation Additions