Improve intermittent waterbody rendering of basins

[jragusa]

Fixes #709

Changes proposed in this pull request:
Add support of basin=detention and basin=infiltration in int_intermittent variable

Test rendering with links to the example places:

basin=detention https://www.openstreetmap.org/way/220462429
Before

After

basin=infiltration https://www.openstreetmap.org/way/234418071
Before

After

basin=infiltration https://www.openstreetmap.org/way/532562272 (no modification)

[kocio-pl]

Just to make it clear: retention basins rendering is not changed, because basin=retention by definition does not loose water, while basin=detention and basin=infiltration do:

https://wiki.openstreetmap.org/wiki/Tag:landuse%3Dbasin#Tags_used_in_combination

[jragusa]

Exactly, basin=retention is not included following your comment. Only basin=detention and basin=infiltration are considered

[jragusa]

@kocio-pl I have updated the description with additional examples

[kocio-pl]

Thanks! This is a simple, but useful change to make people aware of the difference between tagging retention and detention basins.