DateTime & TimeSpan Operation overloads

[DoganCK]

Added operation overloads

• Series<'K, DateTime> - DateTime -> Series<'K, TimeSpan>
• DateTime - Series<'K, DateTime> -> Series<'K, TimeSpan>
• Series<'K, DateTime> + TimeSpan -> Series<'K, DateTime>
• Series<'K, DateTime> - TimeSpan -> Series<'K, DateTime>
• TimeSpan + Series<'K, DateTime> -> Series<'K, DateTime>
• Series<'K, TimeSpan> + TimeSpan -> Series<'K, TimeSpan>
• Series<'K, TimeSpan> - TimeSpan -> Series<'K, TimeSpan>
• TimeSpan + Series<'K, TimeSpan> -> Series<'K, TimeSpan>
• TimeSpan - Series<'K, TimeSpan> -> Series<'K, TimeSpan>
• Series<'K, TimeSpan> + Series<'K, TimeSpan> -> Series<'K, TimeSpan>
• Series<'K, TimeSpan> - Series<'K, TimeSpan> -> Series<'K, TimeSpan>

Added functions

• ScalarGenericOperationL<'T1, 'T2, ‘T3>
• ScalarGenericOperationR<'T1, 'T2, ‘T3>

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I also wanted to add vector operations on DateTime & TimeSpan like:

• Series<'K, DateTime> - Series<'K, DateTime> -> Series<'K, TimeSpan>
• Series<'K, DateTime> - Series<'K, TimeSpan> -> Series<'K, DateTime>

However, I was unable to figure out issues concerning BoxedVectors and writing a generic Vector Operation capable of handling different argument or return types.

Maybe there's a simpler solution for this. Any pointers would be appreciated.

Cheers!