httpupload: Improve error handling

- An error during the upload now no longer hangs everything (GUI changes placed
   in main thread)
 - Some formatting changes
 - Update version in manifest (I think a new minor version is in order for GTK3
   support!)
 - Add self to authors in manifest (shameless plugs, whoop whoop)
 - Remove claim of supporting older versions of gajim

httpupload/manifest.ini

@@ -1,7 +1,7 @@
 [info]
 name: HttpUpload
 short_name: httpupload
-version: 0.4.0
+version: 0.5.0
 description: This plugin is designed to send a file to a contact or muc by using httpupload.<br/>
  Your server must support <a href="http://xmpp.org/extensions/xep-0363.html">XEP-0363: HTTP Upload</a>.<br/>
  Conversations supported this.<br/>
@@ -11,6 +11,7 @@ description: This plugin is designed to send a file to a contact or muc by using
 authors: Thilo Molitor <thilo@eightysoft.de>
  Anders Sandblad <runeson@gmail.com>
  Philipp Hörist <philipp@hoerist.com>
+ Linus Heckemann <linus@sphalerite.org>
 homepage: https://trac-plugins.gajim.org/wiki/HttpUploadPlugin
-min_gajim_version: 0.16.5
+min_gajim_version: 0.16.10
 max_gajim_version: 0.16.10.1