Fixed|Client: Qt warns about unexpected null when disconnecting

The socket is not created until a connection has been made to a server.
Documentation|libdeng2: Fixed a missing @ref target
Shell|GUI: Added a link to Help in the wiki
Shell|GUI: Adjusted menu labels

Used "Server" instead of "Local Server", as the commands may control
remote servers as well.
Shell|GUI|Windows: Fine-tuning for Windows

Changed default console font, removed dialog context help buttons,
changed Preferences to application modal, added a title for the
password query dialog.
Merge branch 'master' into mapdata-c++