Store visited NodeBuilder along with horizon

[frant-hartm]

When a node is reached at horizon 0 it is marked as visited.
After reaching the node again, with horizon >0 its relationships
should be visited.

This commit stores the horizon in CypherContext and uses it to evaluate
if the traversal should continue.

Related Issue

Fixes #407

Motivation and Context

How Has This Been Tested?

unit tests included

Types of changes

• [/] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [/] My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• [/] I have added tests to cover my changes.
• [/] All new and existing tests passed.

[nmervaillie]

LGTM