Request: add functionality to search for part of string via FindNextValue

[jipclaassens]

Now it only works for the exact full string, not a part of the string.

Below it finds 'PerRit' but not 'Per'.

[eoudejans]

DataItemColumn.cpp line 1175 checks for equality:

if (equal_to(searchData[recNo], searchValue))
{
...
}

Which has a specific template implementation for equality between SA_ConstReference and const SharedStr that can be adapted to check for partial equality:

	bool equal_to(SA_ConstReference<char> lhs, const SharedStr& rhs)
	{
		return (lhs.IsDefined() == IsDefined(rhs)) 
			&& equal(lhs.begin(), lhs.end(), rhs.cbegin(), rhs.csend());
	}

[MaartenHilferink]

equal_to should not change, but DataItemColumn could call std::search(... ) if equal_to find failed.

[MaartenHilferink]