add library search functionality

[incertia]

Adds a new argument vector specified with -L or --library to either add a library file or directory.

These "library paths" are then stored in the FileStack and when the time comes to include a file, we first try to resolve the file relative to the current file (current behavior). if that fails, we try to resolve the include in the order the libraries were specified. if the specified library path is a directory, it appends the include path if it does not start with . (this is currently stricter than what circom does) because IMO include "./path" should be meant for local includes only. if the specified library path is a file, we check that the filename is the same as the include path, which should not contain any directory separators.

i believe adding the library files to the FileStack will make the analysis aware of any templates inside, so if there is any additional work please let me know