The input text is now expected to be a toml file with a leading comment
section defining the battle map, according to the following rules:
1. Blank lines are ignored
2. Lines at the top of the file beginning with '#', optionally with
leading spaces, is treated as map data
3. Map data continues until the first line not starting with a #.
4. Any subsequent lines are treated as metadata in toml format.
5. The metadata must contain the [map] section.
6. The [map] section must contain the "name" attribute.
The metadata is available as BattleMap.metadata; the map source is
available as BattleMap.map_string.
New convenience properties ahve been added to the BattleMap class for
accessing portions of the text-only output. This includes the header and
footer attributes.
