Adds Mapping to ETH Futures

[AlexCatarino]

Description

ETHUSDRR represents CME ETH: https://www.interactivebrokers.com/en/trading/margin-futures-fops.php

Fixes GetContractMultiplier GetContractMultiplier was rounding the contract multiplier incorrectly, leading to an unsuccessful contract details request. E.g. LBR multiplier is 27.5 and was converted to "28" instead of "27.5". Instead of rounding all multipliers above 1, we will only round them if the decimal part is zero.

Motivation and Context

Missing mappings. Bug fixing.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] Refactor (non-breaking change which improves implementation)
• [ ] Performance (non-breaking change which improves performance. Please add associated performance test and results)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Non-functional change (xml comments/documentation/etc)

Checklist:

• [x] My code follows the code style of this project.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] My branch follows the naming convention bug-<issue#>-<description> or feature-<issue#>-<description>