docker: Add dockerfiles for running dcrd nodes.

This removes existing dockerfiles and adds new ones.  The removed
dockerfiles were originally used for building the testing images, but
now those images are generated by Docker Hub from the decred/dcrdocker
dockerfiles.

The new dockerfiles provide a way to build an image for running dcrd.
The main Dockerfile runs dcrd inside the same image used for building.
Dockerfile.alpine provides an alternative image that copies the built
files into an alpine based container, removing all build related content
and providing a securer and slimmer alternative.

.dockerignore

@@ -1,2 +1,3 @@
 *~
 vendor
+Dockerfile*

Dockerfile

@@ -0,0 +1,12 @@
+FROM golang:1.10.3
+
+WORKDIR /go/src/github.com/decred/dcrd
+COPY . .
+
+RUN go get -u github.com/golang/dep/cmd/dep
+RUN dep ensure
+RUN go install . ./cmd/...
+
+EXPOSE 9108
+
+CMD dcrd

Dockerfile.alpine

@@ -0,0 +1,19 @@
+# Build image
+FROM golang:1.10.3
+
+WORKDIR /go/src/github.com/decred/dcrd
+COPY . .
+
+RUN go get -u github.com/golang/dep/cmd/dep
+RUN dep ensure
+RUN CGO_ENABLED=0 GOOS=linux go install . ./cmd/...
+
+# Production image
+FROM alpine:3.6
+
+RUN apk add --no-cache ca-certificates
+COPY --from=0 /go/bin/* /bin/
+
+EXPOSE 9108
+
+CMD dcrd

README.md

@@ -13,8 +13,8 @@ dcrd maintains the entire past transactional ledger of Decred and allows
 about Decred please see the
 [project documentation](https://docs.decred.org/#overview).
 
-Note: To send or receive funds and join Proof-of-Stake mining, you will also need
-[dcrwallet](https://github.com/decred/dcrwallet).
+Note: To send or receive funds and join Proof-of-Stake mining, you will also 
+need [dcrwallet](https://github.com/decred/dcrwallet).
 
 This project is currently under active development and is in a Beta state.  It
 is extremely stable and has been in production use since February 2016.
@@ -80,10 +80,59 @@ go install . ./cmd/...
 ```
 
 For more information about Decred and how to set up your software please go to
-our docs page at [docs.decred.org](https://docs.decred.org/getting-started/beginner-guide/).
+our docs page at
+[docs.decred.org](https://docs.decred.org/getting-started/beginner-guide/).
 
 ## Docker
 
+### Running dcrd
+
+You can run a decred node from inside a docker container.  To build the image
+yourself, use the following command:
+
+```
+docker build -t decred/dcrd .
+```
+
+Or you can create an alpine based image (requires Docker 17.05 or higher):
+
+```
+docker build -t decred/dcrd:alpine -f Dockerfile.alpine .
+```
+
+You can then run the image using:
+
+```
+docker run decred/dcrd
+```
+
+You may wish to use an external volume to customise your config and persist the
+data in an external volume:
+
+```
+docker run --rm -v /home/user/dcrdata:/root/.dcrd/data decred/dcrd
+```
+
+For a minimal image, you can use the decred/dcrd:alpine tag.  This is typically
+a more secure option while also being a much smaller image.
+
+You can run dcrctl from inside the image.  For example, run an image (mounting
+your data from externally) with:
+
+```
+docker run --rm -ti --name=dcrd-1 -v /home/user/.dcrd:/root/.dcrd \
+  decred/dcrd:alpine
+```
+
+And then run dcrctl commands against it.  For example:
+
+```
+docker exec -ti dcrd-1 dcrctl getbestblock
+```
+
+
+### Running Tests
+
 All tests and linters may be run in a docker container using the script
 `run_tests.sh`.  This script defaults to using the current supported version of
 go.  You can run it with the major version of Go you would like to use as the