Remove External Zero concept

[Konard]

This branch will no longer exist:

Data/csharp/Platform.Data/Hybrid.cs

Lines 145 to 150 in a670e09

	if (_equalityComparer.Equals(value, default) && isExternal)
	{
	Value = ExternalZero;
	}
	else
	{

No ExternalZero constant anymore:

Data/csharp/Platform.Data/Hybrid.cs

Line 41 in a670e09

public static readonly TLinkAddress ExternalZero = _uInt64ToAddressConverter.Convert(HalfOfNumberValuesRange + 1UL);

Regular (internal) zero becomes external.

Pros:

• Bitwise operations safety
• Better performance with conversion of raw numbers
• Zeros in memory managers are now searchable

Cons:

• Worse performance of memory managers (additional if branches for zero and indexing of zero values)
• Huge change across the codebase

[Konard]

There is a blocker for this issue, at the moment when we start to index zeros we no longer will have multiple links with source and target set to zero, due to limitation of uniqueness.