Add formatting to FooScript

[ludouzi]

Brings formatting support to FooScript using tags such as <b>text</b>. The closing tag is optional, but if not used, everything up to the end of the string will be formatted. Some tags require options to be passed like: <size=14>text. This support greatly simplifies customising playlist presets, and will open up an even deeper level of customisation down the line.

The alternative is to use a QTextDocument in the playlist delegate to draw rich text, but this was found to be significantly detrimental to performance. The performance impact of tags in FooScript is negligible, though it does come with a small memory increase depending on the playlist size and formatting options used. This could be reduced/eliminated by caching the fonts and colours.

This also changes how the script scanner/lexer works. Instead of reading token by token, it tokenises the entire script at setup. This allows parsers to 'peek' ahead, and is required by the formatter in order to properly process tags.