Change hardcoded lucide_en.hlp to reference %LUCIDEHELP% and set variable during install

[Lewis Rosenthal]

This will help with NLS issues, as well.

The goals here are:

1. Move away from a hardcoded filename in lucide.cpp;
2. Allow for appending plugin-specific help guides (and others) to the variable;
3. Allow for substituting any help file for Lucide's help file;

The test WIS currently sets/appends to the following in CONFIG.SYS:

• HELP
• BOOKSHELF
• LUCIDEINSTALLPATH
• LUCIDEHELP

For plugins, the idea is to have plugin authors provide plugin-specific help and to append such files to %LUCIDEHELP% so they are loaded at once. The last page of Lucide's own user's guide will be titled Appendix and contain text indicating that third-party plugin help will appear in subsequent pages.

I have a test help file in progress for the GBM plugin which illustrates this concept.