Add a crash handler to catch uncaught exceptions

This should catch any uncaught exceptions and avoid the Py2Exe message
about Cura.log

Fixes #133

cura/CrashHandler.py

@@ -0,0 +1,41 @@
+import sys
+import platform
+import traceback
+import webbrowser
+
+from PyQt5.QtCore import QT_VERSION_STR, PYQT_VERSION_STR
+from PyQt5.QtWidgets import QDialog, QDialogButtonBox, QVBoxLayout, QLabel, QTextEdit
+
+def show():
+    dialog = QDialog()
+    dialog.setWindowTitle("Oops!")
+
+    layout = QVBoxLayout(dialog)
+
+    label = QLabel(dialog)
+    layout.addWidget(label)
+    label.setText("<p>An uncaught exception has occurred!</p><p>Please use the information below to post a bug report at <a href=\"http://github.com/Ultimaker/Cura/issues\">http://github.com/Ultimaker/Cura/issues</a></p>")
+
+    textarea = QTextEdit(dialog)
+    layout.addWidget(textarea)
+
+    try:
+        from UM.Application import Application
+        version = Application.getInstance().getVersion()
+    except:
+        version = "Unknown"
+
+    trace = "".join(traceback.format_exception(sys.exc_info()[0], sys.exc_info()[1], sys.exc_info()[2]))
+
+    crash_info = "Version: {0}\nPlatform: {1}\nQt: {2}\nPyQt: {3}\n\nException:\n{4}"
+    crash_info = crash_info.format(version, platform.platform(), QT_VERSION_STR, PYQT_VERSION_STR, trace)
+
+    textarea.setText(crash_info)
+
+    buttons = QDialogButtonBox(QDialogButtonBox.Close, dialog)
+    layout.addWidget(buttons)
+    buttons.addButton("Open Web Page", QDialogButtonBox.HelpRole)
+    buttons.rejected.connect(lambda: dialog.close())
+    buttons.helpRequested.connect(lambda: webbrowser.open("http://github.com/Ultimaker/Cura/issues"))
+
+    dialog.exec_()

cura_app.py

@@ -3,7 +3,12 @@
 # Copyright (c) 2015 Ultimaker B.V.
 # Cura is released under the terms of the AGPLv3 or higher.
 
+try:
     import cura.CuraApplication
 
     app = cura.CuraApplication.CuraApplication.getInstance()
     app.run()
+except Exception as e:
+    import cura.CrashHandler
+    cura.CrashHandler.show()
+