Add vfs directory abstraction interface for segments and scorch#75

ajroetker wants to merge 1 commit intoblevesearch:masterblevesearch/bleve_index_api:masterfrom

ajroetker:ajroetker/vfs-scorch-filesystem-abstractionajroetker/bleve_index_api:ajroetker/vfs-scorch-filesystem-abstractionCopy head branch name to clipboard