First pass of changes required for visualization of event-embedding.

First pass of changes required for visualization of event-embedding.

Remove global variable 'AliEveEventManager* gAliEveEvent'.

Instead of this introduce:
a) two private static data-members fgMaster and fgCurrent;
b) a list to hold dependent event-managers.

This is half cooked ... but removal of the global variable calls for
an intermediate check-in.

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Remove obsolete macro trackcount_init.C.