Revert "get source named w/ zero based indices"

This reverts commit 576074aca129988a24efaa4b31857a1666545118.
Revert "add to docstring"

This reverts commit 5d9280a01831867d04f5e2a160ed2f58120df19b.
keep bti_info as private attribute
add prop bti labels
Merge branch 'conserve-4d-ch-names'
remove hack to get chan labels