Switch to a pgsnapshot database instead of an imposm one

This closes #6
delete addresses from import_addresses when they are exact duplicates of existing OSM addresses
Break options into more sensible groups
Change the ewkt option to a WKT option, forcing the use of EPSG:4326 which was implictly required before.
Switch to the single-threaded XML parser from imposm

This is more reliable with strangely formatted XML the speed difference doesn't matter

Fixes #9

This also fixes the issues found in omniscale/imposm-parser#2
Logging fixes
Switch import tag storage in postgresql to hstore

Indexes have also been redone to take into account the new storage

This closes #10
Whitespace fixes
Move parsing to creation of ImportDocument
First pass at change generation logic for missing addr:city

This is the first pass for fixing issue #3. It will detect where an addr:city tag can be added to an existing object and add the information required.

This information is not yet serialized to a .osc file but sufficient information is present within the tables to do so.

This code has not yet been tested for anything other than ways.
Clean up some unnecessary SQL
Add serialization code for changes.

This closes #3 althogh improved documentation and testing is required.
Add diff files to .gitignore
Fix relation change serialization, SQL optimizations