cmd/swarm, swarm/api: bzzr improve + networkid prio

cmd/geth, cmd/swarm: Fix to close file handler appropriately

build: Fix tiny typo

fixes #3444
fixes #3494
networkid override

Added comments to explain why test against 0 appears twice

* Command line overrides saved config, saved config overrides system default

---

fixes #3476
bzzr get with path

Finally a hopefully clean commit for this PR
Added check for empty path to avoid SIGSEGV in path parser and resolver
Added requested tests for empty path and non-existing manifest.
However signature for StartHTTPServer had changed.
Now it's hacked as so:

	StartHttpServer(api.API, &Server{Addr: "127.0.0.1:8504", CorsString: ""})

* Parse url before resolve when path and ENS is supplied, example
* swarm/api/http proxy server test for retrieval of subpath through get
* Removed nil entry assignment on subtrie leaf in recursive key retrieval
* Cleaned up path-or-no-path condition in proxy server get handler
* swarm: processed with gofmt refers to lash/go-ethereum@90daa7a
* swarm: Added public access method Parse alias to parse
* swarm: processed with gofmt References nolash/go-ethereum@2ec3fd7
* Rename parse to Parse, removed alias

web3.js includes bzz methods and throws an error when the extension
module is reregistered. The ENS RPC API is deprecated and not exposed by
anything.

Commit d3b751e4 accidentally deleted a crucial 'return' statement,
leading to a crash in case of an issue with node data. This change
improves the fix in PR #3591 by removing the lock entirely.

containers/docker: update base images, add CA certs, build internally on Ubuntu

* evm: added debug flag (back)

* cmd/evm: gofmt

Gas estimation currently mostly works, but can underestimate for more funky
refunds. This is because various ops (e.g. CALL) need more gas to run than they
actually consume (e.g. 2300 stipend that is refunded if not used). With more
intricate contract interplays, it becomes almost impossible to return a proper
value to the user.

This commit swaps out the simplistic gas estimation to a binary search approach,
honing in on the correct gas use. This does mean that gas estimation needs to
rerun the transaction log(max-price) times to measure whether it fails or not,
but it's a price paid by the transaction issuer, and it should be worth it to
support proper estimates.

The Android NDK was recently removed from gomobile, leading to our Android
builds failing. Starting from https://go-review.googlesource.com/#/c/35173/ ,
gomobile requires a locally installed NDK. This PR ensures that travis installs
that too before running the build steps.

core: removal of dead-code

Removal of dead code that appeard as if we had a consensus issue. This
however is not the case as the proper error catching happens in the vm
package instead.

cmd,eth,les,internal: remove natspec support

* core: Made logging of reorgs more structured, also always log if reorg is > 63 blocks long

* core/blockchain: go fmt

* core/blockchain: Minor fixes to the reorg reporting

accounts, mobile: make account manager API a bit more uniform

common/hexutil: fix EncodeBig, Big.MarshalJSON

The code was too clever and failed to include zeros on a big.Word
boundary.

travis, appveyor, build: add source spell checking