MD tables, codeblocks, quotes, better bold/italic

Added optional support for:
 * Markdown format tables, with bold/italic and inline code in cells.
 * Code blocks with leading tab followed by courier new formatting.
 * Quotes, generated when a line starts with bold italic formatting.
 * Added detection and fixing of broken runs of bold/italic formatting
- e.g. BOLDITALICTEXT: will for some reason end up as two separate
formatted runs in a Google Doc - one for the text, and one for the bold
italic colon.
 * Fixed handling of Courier new text that is also bold and/or italic -
now treated as inline code and formatting ignored, previously was
treated as normal text with formatting applied.