Minor features and bugfixes for desktop version

[dragly]

An improved desktop version is developed in the desktop branch. Most of the changes are done to the MainDesktop.qml file. The following tasks needs to be done:

• New menu needs categories
• Add Recent to Open menu
• Add save button to main view
• Download should categorise available networks
• Upload should redirect to uploaded simulation in downloads view
• Upload should show progress
• Account should include login/signup fields
• Options view needs content
• Split submenus (such as new, save, open) into separate components.