merge: keywords

merge: keywords

 * Make the notmuch tags generic
 * tags: Add index_format %J
 * Add IMAP keywords support
 * Share label editing between imap/notmuch
 * Tidying the code
 * tags: always pass correct buffer length
 * imap: fix memory leak
 * notmuch: remove unused methods declaration
 * tags: remove needs of HEADER_TAGS macro
 * tags: make private method private
 * tags: rename HeaderTag to TagList
 * tags: remove useless ifdef
 * tags: store transformed tags only if needed
 * imap: Don't use keywords terminology, but flags
 * tags: rename OP_MAIN_MODIFY_LABEL/TAGS
 * tags: rename modify-labels/modify-tags
 * tags: rename hdr_tags to driver_tags
 * tags: move tags_editor and tags_commit to mx
 * tags: don't depends on header.c
 * tags: Don't duplicate tags allocation
 * tags: fix notmuch editor return code
 * tags: rename DRIVER_LABEL to DRIVER_TAGS
 * always pass char to mutt_str_append_item