add "soft" require

[mezzodrinker]

Currently, MobTalkerScript allows for the dynamic loading of additional libraries (see also: MtsPackageLib). However, if a library cannot be loaded, an exception is thrown. This may (hard dependencies) or may not (soft dependencies) be intended by the script author.

MobTalkerScript should add another function which allows for soft dependencies to be set up. For example, a function like that could return true or false depending on whether the library could be found and loaded or not and, possibly, another two return values like pcall (exception message and stack trace).