connector/ldap: use gopkg.in/ldap.v2's escape filter

Use the escape filter method provided by the upstream LDAP package
instead of rolling our own.

server: fix expiry test flake

Allow getAttr to return DN

Specify "DN" as attribute name to return, but will only work if not present in ldap.Entry.Attributes
Use when full DN is stored in groupSearch's userAttr

Ensure compared times are within a second of one another instead of
rounding, which can flake if the two times are different enough to
do round to different values.

Tested using the golang.org/x/tools/cmd/stress tool.

The following set of commands fail without this patch:

    $ go get golang.org/x/tools/cmd/stress
    $ go test -o server.test github.com/coreos/dex/server
    $ stress ./server.test -test.run=TestOAuth2CodeFlow
    219 runs so far, 0 failures
    425 runs so far, 0 failures
    618 runs so far, 0 failures
    802 runs so far, 0 failures
    ^C

Closes #699

Enable groups scope

api: add call to list passwords

examples/k8s: update kubernetes examples

*: remove TODO.md file

This existed for when we were developing v2 but v1 was using the
issue tracker. We've since moved these goals to the issue tracker.

Documentation: LDAP connector documentation.

Dockerfile: add OpenSSL to Docker container

connector/ldap: Always set tls.Config.ServerName, to support LDAP ser…

Fix a tyop in the storage documentation

Require the connector to have an ID.

Add OpenSSL to the dex Docker container so wget can be used to query
HTTPS endpoint. This is a requirement for health checking when dex is
doing its own TLS termination.

This increased the image size from 20.37 MB to 20.92 MB (+550 KB).

Additionally add Ed and Rithu as maintainers.

api: add gRPC definition for version endpoint.

Small spelling fix.

README: fix links

README: add link on v2 and section on getting help

*: readme updates for v2

cmd/dex: only expand from env for storages and connectors

server: use seconds instead of nano seconds for expires_in and expiry

Documentation: add doc describing v2 changes