Big refactoring of issues filters

* No magic numbers for issues filtering
* Squash project users selectbox and users selectbox into one class
* Move from API autocomplete to GitLab internal one
* Smarter filter for project/group/all issues
* Use selectbox with searchbox for assignee/author/milestone/label
* Switch to ajax filter for issue author/assignee

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/1035

See merge request !466

* Squash project users selectbox and users selectbox into one class
* Move from API autocomplete to GitLab internal one
* Smarter filter for project/group/all issues
* Use selectbox with searchbox for assignee/author/milestone/label
* Switch to ajax filter for issue author/assignee

Separate Dockerfile for Data and Application

This is based on #1158

Instead of creating data container from same docker image, we create separate docker image for data container to avoid keeping original docker image after upgrading to new version. (That results in 1GB space that cannot be freed)

See merge request !409

Set Application controller default URL options to ensure all url_for calls are consistent

### What does this MR do?

This MR sets the app controller's `default_url_options` so that all `url_for` calls are consistent.

### Are there points in the code the reviewer needs to double check?

Setting these options may simplify `url_for` calls that load the GitLab options already. I did not want to touch existing code yet. I'm also not sure if there are other options that need to be included.

### Why was this MR needed?

If you run GitLab behind a reverse proxy or in a Docker container, you don't want a user to be seeing the local IP and port on which GitLab is running (e.g. 192.168.1.1:8080). Right now there are places where this internal data is leaked (e.g. see the URL in Profile Settings -> Account -> Username; this uses `user_url`).

### What are the relevant issue numbers / [Feature requests](http://feedback.gitlab.com/)?

#1249

See merge request !453