Gas Optimizations

[code423n4]

• CoreCollection: onlyUnInitialized and tokenExists modifier are declared but never used.
• CoreCollection: the internal function _baseURI is declared but never used.
• CoreCollection.setStartingIndex() function can be priavte. (no need to be public)
• ERC721Payable: onlyVaultInitialized modifier is declared but never used.
• Splitter : attemptETHTransfer and amountFromPercent functions are declared but never used.
• • The unchecked block can be used for all the for loops. Consider adding an internal function _increment with an unchecked block and use it to increment the counter inside the for loop.