Now consistently using 'satoshis' and 'bitcoins' (plural).
Removed the term 'decimal bitcoin string'. A bitcoin string can be any decimal format, wheras a 'full bitcoin string' complies to te regex `[0-9]*\.[0-9]{8}`.
Bitcoin parser should accept multiple forms of input (0.25, 1, 6.1234, 0.12345678), noted as TODO.
Added comments.