Support app deployment under a path prefix

Fixes #133

client/components/main/header.jade

@@ -43,10 +43,10 @@ template(name="header")
         the list of all boards.
       if isSandstorm
         .wekan-logo
-          img(src="/wekan-logo-header.png" alt="Wekan")
+          img(src="{{pathFor '/wekan-logo-header.png'}}" alt="Wekan")
       else
         a.wekan-logo(href="{{pathFor 'home'}}" title="{{_ 'header-logo-title'}}")
-          img(src="/wekan-logo-header.png" alt="Wekan")
+          img(src="{{pathFor '/wekan-logo-header.png'}}" alt="Wekan")
 
 template(name="headerTitle")
   h1 {{_ 'my-boards'}}

client/components/main/layouts.jade

@@ -2,12 +2,16 @@ head
   title Wekan
   meta(name="viewport"
    content="maximum-scale=1.0,width=device-width,initial-scale=1.0,user-scalable=0")
+  //- XXX We should use pathFor in the following `href` to support the case
+    where the application is deployed with a path prefix, but it seems to be
+    difficult to do that cleanly with Blaze -- at least without adding extra
+    packages.
   link(rel="shortcut icon" href="/wekan-favicon.png")
 
 template(name="userFormsLayout")
   section.auth-layout
     h1.at-form-landing-logo
-      img(src="/wekan-logo.png" alt="Wekan")
+      img(src="{{pathFor '/wekan-logo.png'}}" alt="Wekan")
     +Template.dynamic(template=content)
 
 template(name="defaultLayout")