parse: Error when stray EndNote and EndText are found

Add True/False as booleans

parse: Add filename to ParseLocation

parse: Use ParseLocation class for line numbers

parse: Add terminator context for statement parsing

parse: Add terminator context for argument parsing

parse: Use meta_context for parse_arguments

ast_types: Move AST data structures to ast_types

parse: Add contexts for tokenizing errors

parse: Pass line and column directly to ParseContext

parse: Throw ParseError on EOF when reading note or text

parse: Create ParseError directly

parse: Clarify value type error message

parse: Improve parser trace logging

parse: Only report expecting symbols for verbs

parse: Use statement context for terminator errors

parse: Disallow non-symbols as verbs

parse: Improve tracing for tokenizer

parse: Shorten text strings properly

parse: Add check for EOF instead of peeking

parse: Move peek back to after next

parse: Detect and skip shebang

parse: Put filename at end of traceback instead of start position

parse: Make parse_file handle the file

parse: Don't lowercase keywords

parse: Improve some parser error messages

parse: Better error messages for set statements

parse: Better error messages for statements

parse: Better error messages for statement arguments

parse: Clarify version handling error message