CodeCoverage: Branch Merge moved to NextOpenCover

Next OpenCover SequencePoint has new Branch(Exit)Coverage attributes.
bec => BranchExitCount
bev => BranchExitVisit
CodeCoverage: Test Next OpenCover binaries
CodeCoverage: FileID/Document SequencePoint Attr

Fixing [CodeContractClass/For] using SequencePoint fileid/url XML
attributes
Using (test) binaries of yet unreleased version of OpenCover (next
version).
CodeCoverage: Use new OpenCover attributes

Now is simpler/cleaner to find start/final SP
Remove obsolete methods & code
CodeCoverage: CCMethod FileID and SequencePoints

CodeCoverageMethod:
New method property .FileID
Filter Visited & Unvisited SP by Method.FileID
CodeCoverage: CCControl SequencePoint filter

CodeCoverageControl: Do not show SequencePoints from another file
CodeCoverage: Remove obsolete BranchPoint code
CodeCoverage: Next OpenCover.Framework.dll
CodeCoverage: Null reference fix, remove Debug ...

CodeCoverageMethodElement:
Null reference thrown because Tests does not contain new attributes,
fixed.
Debug.Fail breaks Test, removed.
CodeCoverage: Test
CodeCoverage: Applied SD5 suggestions
CodeCoverage: OpenCover 4.5.2506 Binaries

https://github.com/OpenCover/opencover/releases/tag/4.5.2506
CodeCoverage: Tests