Fix a bug in the *.spec files and also apply the following major changes:

- Add support for adding the base folder to PATH.
- Only display one pop up window at a time in order to avoid confusion.
- Add automatic updates feature:
	- Windows and Linux versions will be shipped with an updater program used to
	  update both Artemis and the updater itself.
	- MacOs versions will not have the updater. Instead the user will be asked
	  to download the new software version (if present) via browser.

src/executable_utilities.py

@@ -0,0 +1,33 @@
+import sys
+from shutil import which
+import os
+import os.path
+
+
+def _is_executable_version():
+    """Return whether the binary version is running."""
+    return hasattr(sys, "_MEIPASS")
+
+
+IS_BINARY = _is_executable_version()
+
+
+def get_executable_path():
+    """Check whether the executable is in the PATH folder.
+
+    Return the full path or just an ampty string if it is not found
+    in the PATH folder."""
+    path = which("Artemis")
+    if path is not None:
+        return os.path.dirname(path)
+    else:  # Assume that the executable is in the cwd.
+        return os.curdir
+
+
+def resource_path(relative_path):
+    """Get absolute path to resource, works for dev and for PyInstaller."""
+    try:
+        base_path = sys._MEIPASS
+    except Exception:
+        base_path = os.path.abspath(".")
+    return os.path.join(base_path, relative_path)