Add support for is_list to default_from_config.

Parse multiple values from the config file if is_list is True for a
parameter. For example:

[foo]
bar = one
      two
      three
Merge pull request #259 from rocha/list-from-config

Add support for is_list to default_from_config.
Added copy, rename and list methods to S3Client.
Merge pull request #260 from campanja/improve_s3

Add copy, rename and list methods to S3Client.
luigid: allow empty state-path and logdir for development
Merge pull request #261 from miku/fix/empty-options

luigid: allow empty state-path and logdir for development
Document how insignificant parameters work

 * Document how two Tasks with the same params are identical
 * Document how significant=False changes the signature
Merge pull request #262 from onlynone/master

Document how insignificant parameters work