Update app/models/repository.rb

Update doc/install/installation.md

Issue #2699 - Download button not functioning. Replaces slashes with underscore in downloads filename

Line 295: sudo /etc/init.d/gitlab restart
Results in: "Error, unicorn not running!"
This is because unicorn is not yet running for first boot. I suggest changing this to 'start'.

Line 305: sudo apt-get install nginx
Change command to: sudo apt-get -y install nginx
Allowing automated install to simplify and follow pattern of earlier installs.

Render submodule bugfix

Add optional signup

Fix default settings when they are boolean.

error is that ```enabled ||= true``` always evaluates to true.
Change all initialization of bool settings to use the same syntax:
```setting = true if setting.nil?```

Improve setup task, by making it less dangerous

Eliminate horizontal shifting on diff body heights