Command line option to exclude NESTED modules

MNG-5230 added the -pl !g:a switch to exclude explicitly mentioned module g:a, but keep all other modules in the reactor build, including the submodules of g:a.

In some projects there are deeply nested hierarchies of modules just for structuring purposes. In such purely structural needs for hiearchies, it makes sense to exclude the submodules of g:a. Currently the caller must explicitly KNOW and PROVIDE all off them by hand. This is tedious and error-prone.

Hence it would be great if there would be a command line option to turn the "-pl !g:a" switch into a recursive variant that also skips the children and grandchildren of g:a. The optimal solution would be to not add another global switch (like -amb) but to have a flag for each excluded module, like "-pl !+g:a" a plus symbol explicitly enabling recursion ONLY for g:a but not for other modules.