Add convert and save to script.

[foresterre]

Depends on: #10, #36
Todo: look at possibilities, check what works from a usability standpoint.

Make

• convert <format>
  and
• save <file-path>
  part of script.

This might make <out> from sic <in> <out> <options> optional.

save example grammar (simplified, depends on os/filesystem):

whitespace = _{ (" " | "\t" | "\n" | "\r\n") }
sep = _{ ";" }


uint = @{ digit+ }
digit = { '0'..'9' }
path = ${ ( ('a'..'z') | ('A'..'Z') | digit | "." )+  }

operation_sequence = _{ (operation ~ sep?)+ }

operation = _{ blur | flip_horizontal | flip_vertical | resize | save }

blur = ${ ^"blur" ~ whitespace ~ uint}
flip_horizontal = { ^"flip_horizontal" }
flip_vertical = { ^"flip_vertical" }
resize = ${ ^"resize" ~ whitespace ~ uint ~ whitespace ~ uint }
save = ${ ^"save" ~ whitespace ~ path }

main = _{ soi ~ operation_sequence ~ eoi }