Fix term printing in errors to properly show embedded lists

The ~w formatting used before was not printing lists embedded in other
terms. This change uses trunc_io to print those terms safely and without
potentially introducing linebreaks (like ~p would)

Adt fix print bugs

The test if an element in a list was in the printable range didn't
handle the case of a float in the list that compared to be in the
printable range.

Use the io_lib_format:fwrite_g function to print floats

This is superior to float_to_list as it only prints the meaningful
digits and 1.0 isn't rendered as "1.00000000000000000000e+00".

Use lager_trunc_io:format() for all messages submitted via
lager:log().  Also, refactor list flattening and final newline
stripping into shared func that uses re:replace() to do both.

Fixed syntax error w.r.t. configuration example

If backends have a failure or something, don't discard the messages,
wait half a second and then try sending them again.

This solves an issue reported by 'cloudhead' in IRC where deep lists
weren't being flattened when printed with format specifiers like ~s ~p
and ~P, all of which should flatten the list.

Adt add simple rotation

IBM punchcards rejoice! Basho supports your right to continue to affect
how we format source code :)

Adding date spec parsing and calculation of when a spec indicates a file
next needs to be rotated.

az558