[Patch] Imagery providers slippy map enhancements

[Don-vip]

Hi,
Please find attached a proposed patch (V2) to enhance further the one I submitted in #6825.
This patch allows to:

• display several bounds for a single provider (useful for imagery providers that have distinct, non-adjacent, bounds)
• display polygon shapes (it's going to be very useful for the French "GéoLittoral" bounds that cover the entire Atlantic coasts, rather than draw a simple rectangle across all the country)

Here's what it looks like:

The Maps wiki page has to be improved as described in the attached XML file (V2), but this change should be backward-compatible with older JOSM version.

[stoecker]

Did you handle the case, that bounds contains a low resolution all-over-bounds and shape a more detailed one? In this case only the shapes should be displayed.

[bastiK]

What about this format:

    <imagery>
        <entry>
            <name>CRAIG - Auvergne 30 cm</name>
            <type>wms</type>
            <url><![CDATA[http://wms.craig.fr/osm?service=wms&request=getmap&version=1.1.1&layers=auvergne&format=image/jpeg&]]></url>
            <bounds min-lat='44.604' min-lon='2.045' max-lat='46.822' max-lon='4.507'>
                <shape>
                    <point lat='45.4023663' lon='2.4599585' />
                    <point lat='45.4286348' lon='2.3254017' />
                    <point lat='44.9943663' lon='2.0451281' />
                    <point lat='44.6038115' lon='2.1840500' />
                    <point lat='44.6327309' lon='2.5051357' />
                </shape>
                <shape>
                    <point lat='46.3179797' lon='4.0296102' />
                    <point lat='46.4658971' lon='4.0317945' />
                    <point lat='46.5490366' lon='3.7600585' />
                    <point lat='46.7794611' lon='3.6255192' />
                </shape>
            </bounds>
            <attribution-text mandatory='true'>Orthophotographie CRAIG/TopoGEODIS 2009-2010</attribution-text>
            <attribution-url>http://wiki.openstreetmap.org/wiki/WikiProject_France/CRAIG</attribution-url>
            <country-code>FR</country-code>
        </entry>
    </imagery>

After all the shape describes the bounds and you could specify multiple polygons if that is needed.

[Don-vip]

I like it. I will change the format to multiple <shape> inside a single <bounds> tag.
The bounds rectangle will only be displayed if it doesn't contain shapes.