Further bug patches

[cxmeel]

Summary of PR:

• Add global ignores to .GetIgnoredPropertyNames: Globally ignored properties are now included in the .GetIgnoredPropertyNames method of Lib/Properties.lua.
• Fix unsafe name errors: When generating a "safe name" for Instances whose names contain solely unsafe characters, Codify would error out. This closes #21 by mapping unsafe characters to a lowercase alphabet.
• Omit Instance types: If the property's value type is an Instance, it will be omitted from the resulting snippet.
  This does not close #18, but is a temporary fix for this. This will be reassessed later to allow the vanilla snippets to reference Instances if they are in scope.
• Respect original name: When generating snippets that include the .Name property of Instances, the name will now be the same as the original Instance's name, rather than being converted to camelCase.
• Swap Llama for Sift: Llama's now deprecated. Switched to Sift.
• Instance Omission Feedback: A message is now displayed on the home tab to inform users that Instance-based properties will be excluded from the output.