Gas Optimizations

[code423n4]

1. Title : Saving gas by removing = 0

If a variable was not set/initialized, it is assumed to have default value to 0
this implementation was used for saving more gas by removing = 0

##TOOLS USED
Remix, Manual Review

##Mitigation Step
Remove = 0

##Occurances
1. CNft.sol#L49
2. CNft.sol#L97
3. CNft.sol#L119
4. CNft.sol#L175
5. UniswapV2PriceOracle.sol#L41
6. CEther.sol#L178

2. Title : Using short reason string can be used for saving more gas

Every reason string takes at least 32 bytes. Use short reason strings that fits in 32 bytes or it will become more expensive.

##Tool Used
Manual Review

##Occurances
1. CNft.sol#L24
2. CNft.sol#L25
3. CNft.sol#L52
4. CNft.sol#L100
5. CNft.sol#L124
6. CNft.sol#L148
7. CNft.sol#L208
8. CNft.sol#L209
9. /CNft.sol#L279

3. Title : change uint256 i = 0 into uint256 i for saving more gas

https://github.com/bunkerfinance/bunker-protocol/blob/752126094691e7457d08fc62a6a5006df59bd2fe/contracts/Oracles/UniswapV2PriceOracle.sol#L42

using this implementation can saving more gas for each loops.

##Tool Used
Manual Review & Remix

##Recommended Mitigation
Change it

4. Title : Unused SafeTransferFrom() can be removed for saving more gas

since this SafeTransferFrom() function was unused it can be deleted instead for saving more gas cause of recommendation of used safeBatchTransferFrom instead

##Tool Used
Manual Review, Remix