No indent forum style to only have two 'reply' buttons (Bug #1328388)

Instead of having reply buttons next to every post there are only
reply buttons before and after the list. The reply is saved as a child
of the latest existing post so the forum works in a chronological way.

Also added a help file to explain better what the indent options do.

Change-Id: I820a611670e0e1ef5e7a645497c0f223b773c2ae
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>
Merge "No indent forum style to only have two 'reply' buttons (Bug #1328388)"