better indentation controls

There are two relatively simple ways the editor could fairly easily be improved:

1) support auto indenting when editing .pri files. E.g. when specifying mulit-line SOURCES and HEADERS values the subsequent lines should be indented to be under the first line, e.g.

SOURCES+= $$PWD/file1.cpp \
$$PWD/file2.cpp}}

2) Add "Insert Cmd+]" and "Outdent Cmd+[" commands which effect selected content to one of the menus like those provided by Atom and other text editors.