Special rendering for intermittent waterways - fixes #805

Note: there are still some issues.

- (1) - in a rare situation - intermittent waterway with bridge=*, connecting with not intermittent waterway ordering of rendering may be wrong, leading to a small glitch. It is fixable by ordering waterways in SQL querry - but is it worth additional complexity and performance hit to solve something that never appears in data? Or in the worst case - is really rare?
- (2) - is it possible to maintain consistent dashes across (meta)tiles? See the first image.
- (3) - is it necessary to modify rendering of wadis? And derelict canals? Both use dashes,  but wider and  rounded ones. See examples at http://www.openstreetmap.org/way/81918899 and http://www.openstreetmap.org/way/220089162#map=16/31.0738/34.5945

![glitch](https://cloud.githubusercontent.com/assets/899988/4440861/d3433b2e-47ca-11e4-9ea6-0e43613de50e.png)

Examples of a new rendering on an example of http://overpass-turbo.eu/s/5ec (+some minor modifications of OSM data)

Minor waterways:

![z19](https://cloud.githubusercontent.com/assets/899988/4440873/01f99864-47cb-11e4-9483-40c16d3dc661.png)
![z16](https://cloud.githubusercontent.com/assets/899988/4440874/04ac20a4-47cb-11e4-8fed-dc984d85a448.png)
![z14](https://cloud.githubusercontent.com/assets/899988/4440875/06ca1c10-47cb-11e4-8049-46cb2ec558ee.png)
![z13](https://cloud.githubusercontent.com/assets/899988/4440876/087e0a1c-47cb-11e4-979e-4421944a8807.png)
![tunnel](https://cloud.githubusercontent.com/assets/899988/4440877/0a152ff4-47cb-11e4-8b53-a30dfe6f30a1.png)
![bridge](https://cloud.githubusercontent.com/assets/899988/4440878/0b8fcde4-47cb-11e4-9271-e9fc70b97579.png)

Major waterways:
![z19](https://cloud.githubusercontent.com/assets/899988/4440884/15ff8d1e-47cb-11e4-9e00-b40bff158830.png)
![z16](https://cloud.githubusercontent.com/assets/899988/4440885/1722b11c-47cb-11e4-97f0-bb9797d63549.png)
![z14](https://cloud.githubusercontent.com/assets/899988/4440887/185febf8-47cb-11e4-81cd-b96825088b32.png)
![z13](https://cloud.githubusercontent.com/assets/899988/4440888/1a57ebfe-47cb-11e4-8d50-c538e3050c2f.png)
![bridge](https://cloud.githubusercontent.com/assets/899988/4440891/1c77724c-47cb-11e4-81d8-afbd6b90a4b8.png)
![bridge2](https://cloud.githubusercontent.com/assets/899988/4440892/1deb04cc-47cb-11e4-8836-835acb54994b.png)
![tunnel17](https://cloud.githubusercontent.com/assets/899988/4440893/2013bffa-47cb-11e4-8a79-1c58aad6ddb4.png)
![selection_005](https://cloud.githubusercontent.com/assets/899988/4440895/22d7cfa6-47cb-11e4-9802-fad78f055273.png)