[OHM] Military mapping

[Robert Warren]

Here's a sample node, still using bollard instead of the proposal OHM tag namespace.

<node id="2082826810" version="1" changeset="48" lat="50.1633888" lon="3.0499266" user="muninn_project" uid="4" visible="true" timestamp="2013-05-02T15:12:06Z">
<tag k="start_date" v="1917-04-15"/>
<tag k="description" v="Trench Obstacles"/>
<tag k="barrier:barbed_wire" v="yes"/>
<tag k="historic:era" v="ww1"/>
<tag k="barrier" v="bollard"/>
<tag k="comment" v="Experimenting with best means  of identifying trench obstacles"/>
<tag k="fence:pole" v="log"/>
<tag k="end_date" v="1917-04-15"/>
</node>

rhw