dlgWaypointDetails: Applied naming convention
dlgWaypointDetails: Merged duplicate code into loop
dlgWaypointDetails: Added UpdatePage() function

There is no need to call NextPage(0) if we only want to set
the visibilities.
dlgWaypointDetails: Calculate last_page value only once

This value is not changing so we don't need to calculate it every time the
buttons are pressed.
dlgWaypointDetails: Added UpdateZoomControls() function
dlgWaypointDetails: Removed parameters from UpdateCaption() function

There is only one caller and the parameters won't have any other values
than that anyway.
dlgWaypointDetails: Removed duplicate file_num check from UpdateCaption()
Makefile: Renamed $(topdir) to $(PROJ_DIR)
xcsoarswiftsplash.svg: Renamed to logo.svg
resource.h: Renamed IDB_SWIFT to IDB_LOGO