Filter form incorrectly splits TFM when it contains a period

[drewnoakes]

For multi-targeting projects, each target appears as its own node in the graph, as each may have different relationships to siblings.

For example:

• MyNamespace.MyProject(net481)
• MyNamespace.MyProject(net6.0)

The filter dialog splits on periods, meaning that this currently produces a tree resembling:

• MyNamespace
  • MyProject(net481)
  • MyProject(net6
  • 0)