Protect admin api

Admin API now requires a 128 byte base64 encoded secret to be passed in
Authorization header, closing up a potential security hole for those
who expose this service.

server,cmd: Add flag for disabling registation

For situations where admins add users.

db: log schema errors, distinguish them from nil results where needed

Expose API to enable and disable users

includes changes to ensure uniform errors for DB and in-memory repos

build: add equals sign to avoid link warning when building project

Documentation: clearer guidance on creating OAuth 2 client ID

build: vendor quotedprintable to build on Go < 1.5

server: disable users

Provides a more accurate walk through of the screens and menus of the Google
Developers Console encountered whilst creating a client ID.

Fixes #125

Signed-off-by: Chris Swan <@cpswan>

api: don't create a user if you can't send them an email

email/smtp: Fix type comparison error

Fixes #134

server: user management endpoints strictly conform to schema

This change disables the URL fixing behavior or the router associated
with the user management schema. After this commit, URLS routing
to /api/$VERSION/users must target exactly the specified paths. In
addition, `/api/$VERSION/users/` will serve a 404

This change allows users to hit the user create endpoint, which
would previously serve a redirect rather than actually making the
associated change.

Add smtp support

cmd/dex-worker: wait 'til connectors are available

Otherwise, if worker starts without connectors, and then connectors are
added workers have to be restarted to pick up the changes.

Get the K8s files up to date with more docs

Documentation: no need to create a new Google project

A new API key can be generated in an existing Google project

Fixes #123

Signed-off-by: Chris Swan <@cpswan>