Reduce number of ways in low zoom levels

[rurseekatze]

While solving #74, I discovered that there is a huge problem with too big vector tiles on low zoom levels. There should not be more than 10.000 features necessary for rendering just this single tile. In low zoom levels the single ways are simplified, but not merged. This causes that there are thousands of ways that consist of one or two nodes. Merging these short ways to a few longer would reduce the file size.

This issue can be used for collecting ideas on how to reduce the number of features in low zoom levels.

[DerDakon]

The obvious ones are:

• combine ways that end in the same node and have identical tags (bonus points if the result would not be a "v" at places like Hagen-Delstern)
• do the same if the lines just end in nodes which are less than 1 "pixel" away from each other and the way between them has been dropped (thus closing the gaps of small bridges or things like that).