validate boolean attributes

Default branch auto-discovery

Unused routes removed

That was the only place it was used.

As a last resort it was calling a method that didn't exist. Woops!

default_branch now defaults to nil, not 'master'. It will be set after the first
push by discover_default_branch.

Refactor the project clone panel

I have no earthly idea what this file was for, but I couldn't find it being
rendered anywhere.

Replaces two calls that this method simplifies

Add tmp/.gitkeep file to ensure tmp folder exists on clone

Clean up doc/installation.md

Closes #939

The install guide lists it as a requirement, so we might as well have it
by default.

Closes #1072

Changes to text in API documentation

use APP_ROOT in init-gitlab to specify root of project

Change @project instance variable to a local in views/help/markdown

It was erroneously appending the project name to the page's title, even
though the Help system isn't specific to one project.

Update User#identifier to conform to Gitolite 2.x's user pattern

Also modifies the specs a bit because I can't help myself.

Closes #480

[ci skip]