Added ShellSettingsWriter

* can be used via a formatter attribute or by using a target file (location) with ".sh" extension
* Strings and Numbers will be written directly
* Booleans are cast to "1" and ""
* Arrays are written as multiline strings
* Paramaters:
    * use_group_as_prefix: shell varaibles will be prefixed with the settings group, separated by "_" (default: false)
    * capitalize_names: all shell variable names will be uppercased (default: false)
* Tests:
    * simple: tests with no parameters
    * capitalize: tests with capitalize_names=true
    * grouped: tests with use_group_as_prefix=true
Fixed typo and code style warnings
Updated README, AUTHORS and CHANGELOG
Fixed order of authors.
Merge pull request #10 from graste/shell-settings-writer

Shell settings writer