Collaborators have write access as default, and can be changed via repository
collaboration settings page to change between read, write and admin.

This commit improves templates readability, since all of them use consistent
indent with all template command blocks indented too.

1. Indents both HTML containers such as <div>, <p> and Go HTML template blocks
   such as {{if}} {{with}}

2. Cleans all trailing white-space

3. Adds trailing last line-break to each file

Merges repo/sidebar.tmpl with repo/header.tmpl and makes every repo page use
middleware.RepoRef() necessary to display information on this menu.

This is more inline with way GitHub looks like and feels much more natural and
in style with rest of the interface.

- update locales
- update README

The normal go get protocol is to show the go-import meta tag when ?go-get=1 is appended to the url. This commit implements that behaviour and cleans the go-get option from the repository settings page.