Build batch file tweaks & level select editing improvement

A few little things in here, starting with the Windows build batch files:
*   The ROM split scripts have been updated to reflect what's contained and referenced within the actual disassembly - this means fixing the oddly named "Normal Text.bin hi" and removing a couple of S3 DAC headers that are no longer referenced.
*   The .bat versions of the build scripts now produce the same output filenames as the .py versions do.
*   AppendS3.bat now produces the same filename as buildS3Complete.bat (sonic3k.bin)
*   Retention of the previous build in buildS3Complete.bat has been fixed (the filenames in this section presumably weren't updated when copied from buildSK.bat).
*   All the output files generated by these scripts have been added to .gitignore.
*   The batch files no longer fail if called from a working directory other than the one they reside in.  This is done with the magic %~dp0 (and pushd/popd) which should work in any relevant version of Windows NT, but not the old 9x series if anyone cares about that.
*   Standardised all the .bat path separators as \ instead of /, as it's Windows' standard and I doubt anyone's going to be running the .bat version of the builds on other platforms.

I've also introduced the macro I use for simply editing the level select text - these changes allow you to edit the strings directly in the disassembly by making use of the codepage/charset features of AS.

Naturally, skbuilt.bin remains bit perfect.

I appreciate I could just push this, but I like the idea of at least having some extra eyes on it first.  Cheers.