64bit support
osmjs: enable absolute paths for the .js file
Changes needed to OGR code for 64 bit IDs.

The OGR library doesn't support 64 bit integers. So we have to either use
doubles to represent large IDs or we stay with the 32 bit integers where we are
sure that the IDs are small enough, ie. for ways and relations.
Fix filter_and_accumulate() and use VARCHAR for long ids.
Use string columns for node ids in js examples
Merge pull request #62 from simon04/osmjs_absolute_path

osmjs: enable absolute paths for the .js file
Fix for #61. Missing after and before callbacks in js handler
Fixed callback documentation
README update, release example code into PD
Merge remote branch 'upstream/master'
Use string columns for IDs in places.shp