core, eth, rpc/api: rpc method to inspect the txpool queue

p2p/discover: fix Windows-specific issue for larger-than-buffer packets

containers/docker/master-alpine: add the legacy gmp lib back for now

containers: regroup and add Alpine images (31 MB)

internal/debug: APIs for profiling and tracing

core, core/types, miner: fix transaction nonce-price combo sort

The debug package provides an RPC wrapper for glog settings and the
debugging facilities of the Go runtime. They can be triggered through
both command line flags and the IPC listener.

The "result" field of JSON-RPC 2.0 responses was omitted
if the result was nil, causing exceptions in web3.js.

Rpc2 console

logger/glog: improve vmodule

On Windows, UDPConn.ReadFrom returns an error for packets larger
than the receive buffer. The error is not marked temporary, causing
our loop to exit when the first oversized packet arrived. The fix
is to treat this particular error as temporary.

Fixes: #1579, #2087
Updates: #2082

separate and optimize Dockerfile for master and develop

This change allows setting the verbosity for directory prefixes
using the syntax:

    --vmodule=eth/=6

core/vm: resolve circular dependency to debug vm storage

console: add admin.sleep and admin.sleepBlocks

Nodeinfo format Genesis and Header

core/state: always commit in batches, just finish if not needed later

core: fix invalid state reuse in chain maker based tests

common: Fix HomeDir detection

I am working on porting geth to [Ubuntu Core](https://developer.ubuntu.com/en/snappy/https://developer.ubuntu.com/en/snappy/). I am testing geth on a Raspberry PI and for Ubuntu Core the $HOME directory is unique for each application. See [here](https://developer.ubuntu.com/en/snappy/guides/filesystem-layout) for more information of their filesystem layout.

For some reason in Go `usr.HomeDir` returns a different value than `$HOME` in Ubuntu Core.

Adding this at the end of `HomeDir()`
```go
fmt.Printf("at HomeDir, user.HomeDir = %s and $HOME is %s\n", usr.HomeDir, os.Getenv("HOME"))
```

gives the following output

```
at HomeDir, user.HomeDir = /home/ubuntu and $HOME is /home/ubuntu/apps/geth.sideload/IJcODREBYbHO
```

With this commit, I propose giving precedence to the `$HOME` environment variable as is also suggested by the [homedir](https://github.com/mitchellh/go-homedir/blob/master/homedir.go) project.

core, eth/downloader: ensure state presence in ancestor lookup

core: transaction invalidation and reorganization fixes

eth/downloader: throttling tests are time-sensitive, don't run parallel