storage: increase the number of bytes randomly generated for IDs

dev branch: add a simple gRPC API

server: add a test for the health check handler

storage/sql: enable garbage collection

Was an oversite of the initial SQL PR.

Because these values are used for OAuth2 codes, refresh tokens,
etc, they shouldn't be guessable. Increase the number of random
bytes from 64 to 128.

cmd/dex: rename file

dev branch: add SQL storage implementation

This change adds support for SQLite3, and Postgres.

Currently, whether or not a user has authenticated themselves through
a connector is indicated by a pointer being nil or non-nil. Instead
add an explicit flag that marks this.

dev branch: add TODO file

dev-branch: generate string literals instead of escaped strings

When compiling the default templates into the source code, use
string literals instead of escaped strings to reduce merge
conflicts.

dev branch: port templates from master branch

Add a small program to iterate over the templates directory and
generate a go map of name to file data. This is so we can compile
these templates into the dex binary instead of requiring files on
disk.

Also add a Makefile rule to do this automatically.

Since we don't have a good strategy which takes a username and password
add a mock connector which implementes PasswordConnector so we can
develop the frontend screens.

dev branch: set response types supported in discovery based on server config

While the issue tracker is being used for the master branch, add a
TODO file to record work to do on this branch. Issues are currently
unprioritized and do not indicate requirements for any particular
milestone.