Clean up the launcher script, and some other bits.

novelWriter.py

@@ -3,10 +3,6 @@
 
 import sys
 
-if sys.hexversion < 0x030600F0:
-    print("ERROR: At least Python 3.6 is required")
-    sys.exit(1)
-
 try:
     import PyQt5.QtWidgets
     import PyQt5.QtGui
@@ -15,18 +11,6 @@ except:
     print("ERROR: Failed to load dependency python3-pyqt5")
     sys.exit(1)
 
-try:
-    import PyQt5.QtSvg
-except:
-    print("ERROR: Failed to load dependency python3-pyqt5.qtsvg")
-    sys.exit(1)
-
-try:
-    import lxml
-except:
-    print("ERROR: Failed to load dependency python3-lxml")
-    sys.exit(1)
-
 if __name__ == "__main__":
     import nw
     nw.main(sys.argv[1:])