Improve handling of keywords

[Cypher1]

Also updates and improves some example code with planned features:

• Make example syntax more consistent
• Chmod examples for the interpreter
• Add shebangs
• Add instances examples
• Make reserved keywords file into a raw txt file
• Reserve more keywords for future use
• Add use and provide keywords and set them up in the string interner
• Use include_strs to avoid lazy_static for KEYWORD list
• Prefix StringInterner keywords properties to avoid clash with rust keywords