Gns3-gui

* Fix issue when asking to run the setup wizard again. Ref 2846
* Remove warning about VirtualBox not supporting nested virtualization. Ref https://github.com/GNS3/gns3-server/issues/1610
* Ask user if they want to see the wizard again. Ref 2846

* Revert to jsonschema 2.6.0 due to packaging problem.

* Bump jsonschema to version 3.0.2
* Fix "Unable to change Remote Main Server IP". Fixes 2823
* Fix "AttributeError: 'QGraphicsTextItem' object has no attribute 'locked'". Fixes 2814
* Fix a minor typo in the setup wizard

* Fix issue preventing to open the QFileDialog in the correct directory.
* Remove unused edit readme action. Fixes 2816
* Remove deprecated Qemu parameter to run legacy ASA VMs. Fixes 2827
* Upload images on remote controller. Fixes 2828
* Preferences dialog: send API request only if connected to controller
* Fix AttributeError: 'QGraphicsTextItem' object has no attribute 'locked'. Fixes 2814
* Fix KeyError: 'chassis' when converting old IOS templates. Fixes 2813

* Fix template migration issues from GUI to controller. Fixes https://github.com/GNS3/gns3-gui/issues/2803
* %guest-cid% variable implementation for Qemu VMs. Fixes https://github.com/GNS3/gns3-gui/issues/2804
* Increase timeout from 2 to 5 seconds for synchronous check. Ref 2805

* Fix KeyError: 'endpoint' issue. Fixes 2802
* Fix wrong aligment of symbols in saved/exported projects. Fixes 2800
* Replace urllib.request by Qt implementation for local server synchronous check. Fixes 2793
* Support snapshots for portable projects. Fixes https://github.com/GNS3/gns3-gui/issues/2792
* Fix event notification problem for projects and how snapshots are restored.
* Do not close the nodes dock widget when creating project.
* Fix no scan for images on remote controller. Fixes 2799
* Use QNetworkAccessManager to download custom appliance symbols.
* Experimental auto upgrade should not be available for "frozen" app. Fixes 2797
* Don't allow link labels to be moved for locked nodes. Fixes 2794
* Catch more OSError/PermissionError when checking md5 on remote images. Fixes 2582
* Fix exception when grid size is 0. Fixes 2790
* Catch PermissionError when scanning local image directories. Fixes 2791