Packaing on Windows and fix .rc issues for MSVC build.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Fix MSVC compiler warning
Add CMake macro to check repo status.
Minor changes
Add CMake script to check repository status.
Fix some problems with wxWidgets version selection.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Factor out the TB icon / info panel from the WelcomeFrame so that it can be reused in the about frame.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Added an about frame.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Add "About TrenchBroom" menu item to help menu on Linux and Windows.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>