Merge branch 'frontier/natspec' of https://github.com/ethersphere/go-ethereum into ethersphere-frontier/natspec

- simplify resolver and tests
- added missing test for KeyToUrl
- fix notice error message and its test with !%x(MISSING)
- natspec test: insertTx modified - does not prepend 0x to contract address
- disable networking in e2e test

- add resolver tests and fix resolver to pass
- statereg constructor fixed
- comments added to natspec plus docserver integration for natspec userdoc fetching

- statereg methods move to natspec/resolver/docserver
- fix failing test on invalid js input

fixed 2/3 tests

- constructor takes abidoc, userdoc
- json parsing of userdoc
- method found by abi data
- notice found from method