Support restricting to specific section type

To folio-current-section and folio-section-bounds add an optional
argument for restricting the scope to specific section type such as
only chapters.
Add defuns for moving to next or previous section type

Optionally instead of moving point just return the point position of
start of the next or previous section.
Add folio-with-disabled-undo

for temporarily disabling the recording of the undo history for a list
of body forms.
Disable undo history recording when un-/indexing