Support for indent-after-parens astyle option

Summary:
This change adds --indent-after-parens and --indent-continuation support in the custom astyle formatter config.
(see: http://astyle.sourceforge.net/astyle.html#_indent-after-parens)

Reviewers: #kdevelop, mwolff

Reviewed By: #kdevelop, mwolff

Subscribers: mwolff, kdevelop-devel

Tags: #kdevelop

Maniphest Tasks: T10373

Differential Revision: https://phabricator.kde.org/D18371