Add eclipse project files to .gitignore

Like some of the other projects (nova, heat, oslo, cinder) git ignore
eclipse project files. This will remove manual steps for people
developing from eclipse.

Change-Id: Ib908c8d419072b440f5ec647bea8f13b97e48f7c
Merge "Add eclipse project files to .gitignore"
Verify for duplicate location+metadata instances

Glance allow users to have duplicated locations for the same image. This
could led to some confusion and bad UX. This patch introduces such check
in the insert method and makes both extend and append use it to add new
images.

The patch also adds a new exception - DuplicateLocation - and handles it
in the v2 of the API. When `DuplicateLocation` is raised, a BadRequest
will be returned back to the client.

A new test for this functionality was added as well.

Change-Id: I32400d467408e3d56bbbdbb3379357f2ee812e56
Closes-bug: 1251244
Merge "Verify for duplicate location+metadata instances"