build: rename swarm deb package to ethereum-swarm; change swarm deb version from 1.8.x to 0.3.x (#16988)

* build: add support for different package and binary names

* build: bump up copyright date

* build: change default PackageName to empty string

* build, internal, swarm: enhance build/release process

* build: hack ethereum-swarm as a "depends" in deb package

* build/ci: remove redundant variables

* build, cmd, mobile, params, swarm: remove VERSION file; rename Version to VersionMeta;

* internal: remove VERSION() method which reads VERSION file

* build: fix VersionFilePath to Version

* Makefile: remove clean_go_build_cache.sh until it works

* Makefile: revert removal of clean_go_build_cache.sh

This commit adds all changes needed for the merge of swarm-network-rewrite.
The changes:

- build: increase linter timeout
- contracts/ens: export ensNode
- log: add Output method and enable fractional seconds in format
- metrics: relax test timeout
- p2p: reduced some log levels, updates to simulation packages
- rpc: increased maxClientSubscriptionBuffer to 20000

Smaller size on mobile is always good.
Might also solve our maven central upload problem

* build: add GOBIN to PATH for gomobile

* build: install gobind alongside gomobile

* crypto/bn256: full switchover to cloudflare's code

* crypto/bn256: only use cloudflare for optimized architectures

* crypto/bn256: upstream fallback for non-optimized code

* .travis, build: drop support for Go 1.8 (need type aliases)

* crypto/bn256/cloudflare: enable curve mul lattice optimization

This avoids setting CC for the go run invocation, which fails on go1.10.

* build: enable unconvert linter

 - fixes #15453
 - update code base for failing cases

* cmd/puppeth: replace syscall.Stdin with os.Stdin.Fd() for unconvert linter

* build: [finishes #15372] implements generalized linter and travis job

* .travis, build: minor polishes, disable deadcode

Tests are now included as a submodule. This should make updating easier
and removes ~60MB of JSON data from the working copy.

State tests are replaced by General State Tests, which run the same test
with multiple fork configurations.

With the new test runner, consensus tests are run as subtests by walking
json files. Many hex issues have been fixed upstream since the last
update and most custom parsing code is replaced by existing JSON hex
types. Tests can now be marked as 'expected failures', ensuring that
fixes for those tests will trigger an update to test configuration. The
new test runner also supports parallel execution and the -short flag.

Also add the package to the license tool ignore list.