Move all logo/splash images to the resource file

Much easier to update/modify the images, and also easier to address
non-96dpi issues at run-time.  Also, less .frx files!
Initialize GDI+ earlier in the program load process

We need GDI+ to pull non-BMP files from the resource file, so we can
properly render the splash screen.  That means we need GDI+ right as the
program starts.

Also, a global GDI+ availability variable, separate from the image
save/load engine, is now available for use.  (Previously GDI+ was used
only for image load/save, but now it is much more deeply entrenched.)
If loading a VB-compatible image from the resource file, use VB-only methods
Add DPI conversion functions to the interface module

Relevant to #83.

PD's layout uses many hard-coded pixel measurements, as specified at 96
dpi.  Other DPIs will result in faulty layouts.

I am now wrapping all hard-coded pixel measurements in these fixDPI()
calls, which will save me from redoing all my measurements, and
guarantee proper layouts on all DPIs.
Fix DPI issues on splash screen

Relevant to #83.

Also, note that the splash image is now stored in the resource file.
Fix DPI issues on About screen, and improve credit appearance

Relevant to #83.

Also, a mask is now used for better scroll results.
Fix some DPI issues on Main form

Relevant to #83.

This was a quick once-over - additional issues may persist.  I'll check
in greater detail later.
Fix DPI issues on all custom PD user controls

Relevant to #83.