Offer list of detected makefiles to allow choosing of root makefile

[andreeis]

We could detect all makefiles present below the root, offer them in a list to chose one as a root makefile (or even multi-choice, to wrap more than one under one central main makefile).

[gcampbell-msft]

Going ahead and closing this issue. 363d0fa implements activating on makefiles below the root.

[andreeis]

I still think the second half is worth keeping (or creating a new item.. again 2 items in one ticket :) ).

[gcampbell-msft]

I updated the title and will label and re-open.