Updated NaSC to 0.7.1 which includes multiple new features.

Changelog:

• You can now manage multiple calculation sheets - load, add, remove and rename sheets.
• Fixed a bug that should make NaSC much more stable.
• Save sheets dynamically.
• Removed auto complete functions with parenthesis.
• Preperation to make NaSC translatable.

Tested 0.7.2 by running through the tutorial and doing a set of example calculations. Everything looked and functioned as expected.