Vertex-track association tool implementation

[dcentanni]

This version features an optimized tool for finding the most compatible and closest parent track for neutral-like "orphan" vertices. An overview follows:

• The closest track is found in the neighbourhood of the vertex according to emvertex.trfit.r2max and emvertex.trfit.dzmax parameters set in the vertex.rootrc file
• The track is splitted in two tracks given the position (in Z) of the vertex
• The segments belonging to each track are fitted
• Tracks are attached to the vertex
• Vertex parameters are updated, flag is set accordingly
• A new vertex file is produced containing re-flagged vertices, genuine neutral-like vertices as well as genuine charged vertices.

The feature can be triggered using -fit flag from the command line when launching emvertex application.