Expand the summary buffer vertically.
Add olm-folder-name and olm-init.
Display the current folder name on the olm-summary-mode line.

* Originally it was displayed on the olm-message-mode line.
Stop killing the draft bafter right after saving it.
Fix the bug that causes mail save failure.

* EntryID must be at a first line of a buffer.
Add Olm.default_folder_id.