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/versioncontroller.py

@@ -0,0 +1,111 @@
+from io import BytesIO
+import json
+from constants import Constants
+from os_utilities import get_os
+from web_utilities import download_file
+
+
+"""This module exposes just one class: VersionController.
+
+All the relevant information can be accessed with the dot notation on an instance of such class, e.g.:
+               version_controller.software.hash_code
+is the hash_code of the latest release of the software running on the current OS."""
+
+
+def _download_versions_file():
+    """Download the json file containing all the information
+    about the latest version of the software. Return a dictionary
+    containing only the information for the running OS.
+
+    Return a dictionary from a json with the following structure:
+    {
+        "windows": {
+            "software": {
+                "version": "...",
+                "url": "...",
+                "hash_code": "...",
+                "size": ...
+            },
+            "updater": {
+                "version": "...",
+                "url": "...",
+                "hash_code": "...",
+                "size": ...
+            }
+        },
+        "linux": {
+            "software": {
+                "version": "...",
+                "url": "...",
+                "hash_code": "...",
+                "size": ...
+            },
+            "updater": {
+                "version": "...",
+                "url": "...",
+                "hash_code": "...",
+                "size": ...
+            }
+        },
+        "mac": {
+            "software": {
+                "version": "...",
+                "url": "...",
+                "hash_code": "...",
+                "size": ...
+            },
+            "updater": {
+                "version": "...",
+                "url": "...",
+                "hash_code": "...",
+                "size": ...
+            }
+        }
+    }
+    """
+    try:
+        version_dict = json.load(
+            BytesIO(download_file(Constants.VERSION_LINK))
+        )[get_os()]
+    except Exception:
+        return None
+    else:
+        return version_dict
+
+
+class VersionController:
+    """Dynamically create attributes corresponding to elements of a dictionary.
+
+    Used to get updates information."""
+
+    def __init__(self, dct=None):
+        """Initialize the dictionary"""
+        super().__init__()
+        self._dct = dct
+
+    def __getattr__(self, attr):
+        """Override super().__getattr__. Dynamically create new attributes
+        corresponding to elements of the diciotnary."""
+        if self._dct is None:
+            if not self.update():
+                return None
+        try:
+            dct_element = self._dct[attr]
+        except Exception("ERROR: Invalid attribute!"):
+            return None
+        else:
+            if isinstance(dct_element, dict):
+                setattr(self, attr, type(self)(dct_element))
+            else:
+                setattr(self, attr, dct_element)
+            return getattr(self, attr)
+
+    def update(self):
+        """Reset the dictionary to the correspondig json file containing
+        the latest version information. Call this function inside a Qthread."""
+        dct = _download_versions_file()
+        if dct is not None:
+            self._dct = dct
+            return True
+        else:
+            return False