Fix #2: crash when returned list / matrix is empty
Remove comment mentioning EVAL_BOOL_EXPR

EVAL_BOOL_EXPR and its siblings are for the GAP language interpreter,
and not for converting between C/C++ booleans and GAP booleans.
Remove NormalizTest
Fix indention
Change parameter names and error messages to adhere to GAP conventions

In GAP, the rough convention is that public identifiers are in camel
case, with functions starting with uppercase, while variables start
with lowercase.

Hence, change parameter names like "Cone" to "cone".

Also, adapt various ErrorQuit messages to refer to the parameter names.
Rename NormalizCone to NmzCone
Add NmzHasConeProperty and NmzConeProperty