update: improve retry logic in import loop

- reconnect to DB before retry
- fix retry delay
- stop progress on error

fixes #302

expire: ignore changes outside of webmercator boundaries

update: update go-osm with fix for stray state.txt files

build: update build dependencies for binary releases

github: update deprecated actions

readme: update performance section with recent import time

dev: update packaging script

mapping: fix (way)zorder for non-int32 layer values

build: drop support for go 1.9; test with 1.14 and 1.15

build: update leveldb/geos