Add task to generate images from SVG and change to new logo (#2194)

* Add makefile task to generate images from SVG and change to new logo

* use absolute path on generate-images

templates/base/head.tmpl

@@ -90,7 +90,7 @@
 						<div class="column">
 							<div class="ui top secondary menu">
 								<a class="item brand" href="{{AppSubUrl}}/">
-									<img class="ui mini image" src="{{AppSubUrl}}/img/favicon.png">
+									<img class="ui mini image" src="{{AppSubUrl}}/img/gitea-sm.png">
 								</a>
 
 								{{if .IsSigned}}