Allow config_file to be a path-like object

[mwtoews]

Currently XmiWrapper.initialize(config_file) only accepts str type. Attempting with a path-like object looks like this:

from pathlib import Path
sim_dir = Path("/path/to/sim")

obj = CustomXmiWrapper()
obj.initialize(sim_dir / "config.yaml")

File D:\src\xmipy\xmipy\xmiwrapper.py:140 in initialize
self._execute_function(self.lib.initialize, config_file.encode())

AttributeError: 'WindowsPath' object has no attribute 'encode'

This PR enables config_file to accept path-like objects too, using the preferred os.fsencode method to convert it to bytes.

Other changes in this PR change typing hints Path with PathLike, as there are several other classes that enable path-like interfaces.

Unfortunately, there is not easy place to add a test for this enhancement. Suggestions welcome!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4bd60ee) 87.50% compared to head (4ec0c3c) 87.52%.

@@             Coverage Diff             @@
##           develop     #128      +/-   ##
===========================================
+ Coverage    87.50%   87.52%   +0.02%     
===========================================
  Files            7        7              
  Lines          520      521       +1     
===========================================
+ Hits           455      456       +1     
  Misses          65       65              

Files	Coverage Δ
xmipy/xmiwrapper.py	87.33% <100.00%> (+0.03%)	⬆️

[Hofer-Julian]

Thanks!