MAINT-4077: Refactoring to add copy constructors to the LLVisualParam class and all of its derived descendants in order to clarify ownership of memory pointers.

consolidated most indra-specific constants in llcommon under indra_constants.h
fixed issues with operations on mixed unit types (implicit and explicit)
made LL_INFOS() style macros variadic in order to subsume other logging methods
such as ll_infos
added optional tag output to error recorders

A couple of merge issues that caused the resulting code to not build.

Moved over the necessary classes to llappearance to support the loading of the
avatar's structure & params from file.