Heads-I-Lose

As per the Encoded Polyline Algorithm Format page:
https://developers.google.com/maps/documentation/utilities/polylinealgorithm

- Previously the decoder only worked with a single point (baby steps and
all that) and was tested with the example point of `~oia@
- This commit extends it to work with the example of
_p~iF~ps|U_ulLnnqC_mqNvxq`@
- Probably still to do is figure out decoding an unsigned value and the
bit about string literals.

Basically alter functions to use a list of lists approach:

- Adds split_up_six_bits which does what it says on the tin and looks
for the absence of the 0x20 bit and creates a list of lists of each
point's bit chunks.
- five_bit_chunks is now called six_bit_chunks since the groups of
chunks have to be split up at the six bit stage.
- Similarly, five_bit_chunk is now called six_bit_chunk; it is otherwise
exactly the same except from not "un-or-ing" the 0x20 bit to go from
six bits to five bits. Still padding to six bits, but I wonder if this
is entirely unnecessary and I can use this to determine the absence of
the 0x20 bit and thus where to split up the chunks into groups?
- five_bit_chunks now does the "un-or-ing" by mapping over the list of
lists. Perhaps this could be bundled in with the rest of the big
lists:map in the top level decode function?
- most of what was in the top level decode function remains the same,
but is just mapped over a list now. These should probably be at least
pulled out as separate functions that are mapped over. Need to decide
which approach to go for: functions that map or mapping functions.
- Changes to reversing, specifically the un-reversing of the five bit
chunks. This was bundled in with the five_bit_chunks function and the
un-reversing was achieved by simply not doing lists:reverse since the
function naturally reversed it. Now, to follow the algorithm backwards
step by step, there is now a lists:reverse at the end of
six_bit_chunks which then has to be undone by including a
lists:reverse in five_bit_chunks.
- Add in algorithm step numbers to comments. Leaf check-in: 8d51987b6f user: base@atomicules.co.uk tags: polyline, trunk