Two factor authentication support (#630)

* Initial commit for 2FA support

Signed-off-by: Andrew <write@imaginarycode.com>

* Add vendored files

* Add missing depends

* A few clean ups

* Added improvements, proper encryption

* Better encryption key

* Simplify "key" generation

* Make 2FA enrollment page more robust

* Fix typo

* Rename twofa/2FA to TwoFactor

* UNIQUE INDEX -> UNIQUE

templates/user/settings/twofa_enroll.tmpl

@@ -0,0 +1,33 @@
+{{template "base/head" .}}
+<div class="user settings delete">
+	<div class="ui container">
+		<div class="ui grid">
+			{{template "user/settings/navbar" .}}
+			<div class="twelve wide column content">
+				{{template "base/alert" .}}
+				<h4 class="ui top attached header">
+					{{.i18n.Tr "settings.twofa_enroll"}}
+				</h4>
+				<div class="ui attached segment">
+					<p>{{.i18n.Tr "settings.scan_this_image"}}</p>
+                    <img src="{{.QrUri}}" alt="{{.TwofaSecret}}">
+                    <p>{{.i18n.Tr "settings.or_enter_secret" .TwofaSecret}}
+                    <p>{{.i18n.Tr "settings.then_enter_passcode"}}
+                    <form class="ui form" action="{{.Link}}" method="post">
+						{{.CsrfTokenHtml}}
+						<div class="inline required field {{if .Err_Passcode}}error{{end}}">
+							<label for="passcode">{{.i18n.Tr "passcode"}}</label>
+							<input id="passcode" name="passcode" autofocus required>
+						</div>
+						<div class="inline field">
+							<label></label>
+							<button class="ui green button">{{.i18n.Tr "auth.verify"}}</button>
+						</div>
+					</form>
+				</div>
+			</div>
+		</div>
+	</div>
+</div>
+
+{{template "base/footer" .}}