Replace Global References in IPM with Macros

[isc-kiyer]

Currently, many parts in IPM are using direct global references instead of macros. Which makes things hard to manage.

For example, in %IPM.Extension.SourceControl.Perforce.Main, ^Sources(0,"FileTimeStamp",tName_".ZPM"), etc.

We should change them to macros to keep track of them cleanly.