Alpha 2 "Ballard" (2021.01)

Second alpha version of the engine library, to be used with the second alpha of the Imprimis game.

Changelog:

• Many min max ceil floor abs fabs functions changed to std:: equivalent
• Many inline extern statements moved to headers instead of in code files
• Macro indentation improvements
• Many ICOMMAND references converted to COMMAND or COMMANDN for future removal of ICOMMAND
• Use of inline const references in headers to replace those in code files
• Fixed sound.h textedit.h lacking header guards
• Removed wav audio file support
• Most NULL statements removed, replaced with nullptr
• Windows build configuration added (static library)
• Unused glassenv code removed
• Command argument flag documentation improvements
• Command COMMANDN macro documentation improvements
• C++ style type casting in stream.cpp