Documentation: remove reference to DEX_APP_REDIRECTURL

Fix response_type missing param

This commit fix problem with response_type param, which is required according to OIDC spec, when it is missing.
 At now, when connector_id url query param is not set, connector view use response_type that client request instead of default "code".

Fixes #370

*: remove build-units script

server: add db heatlh checker to server checkers

move outside dependencies to ./vendor directory

Documentation: update roadmap for 0.4 release cycle

closes #328

Fixes #365

server: url decode basic auth credentials

Fixes #336

integration: fix email case sensitivity test

add support for resend an invite email

db: email comparison should be case insensitive

Fix cross compilation

When reading migrations from files, sql-migrate attempts to split
SQL statements. The parsing logic does not handle $BODY$ statements
and broke when the migration included one.

Replace go-bindata with a small migration generation script and use
in memory migrations instead.

Fixes #338

*: remove unused code

This change has no functional changes, it only removes dead code.

This change solves the User's API problem when you want to create an user that its email hasn't been verified yet but it exist.
At now, you can resend invitation email using endpoint /users/{id}/resend-invitation

Fixes #184

closes #159

db: only allow one open connection for in memory databases