Enhancement to the format of the .addins file

[CharliePoole]

The root .addins file often contains multiple entries starting with varying counts of ../, like ../../XXX, ../../../XXX, etc. We can simplify the files in most cases by defining a new pattern ^^/, which means "any number of ../ repeated. This is essentially the same logic as our use of **/ but working upward rather than downward in the directory structure.