Added section on conditional inclusion to MWEL docs
Added section on conditional inclusion to MWEL docs

Along with 538fd44bc94d36e51a821d0dd28cf117ec7609db, closes mworks/mworks-issues#330

mworks/mworks,mworks/mworks,mworks/mworks,mworks/mworks,mworks/mworks,mworks/mworks,mworks/mworks,mworks/mworks,mworks/mworks