Improve config module testing
Add output context options for searches

Add the grep like -A, -B and -C options to `afind search` as well as the
server side functionality to implement it. New unit tests pass but wider
testing is required as although the zero context output has not changed,
-C=1 produces at least two lines of context, and nearby match lines have
an impact on the total number of context lines, suggesting some bleeding
between groups is occuring.
Merge branch 'master' of https://github.com/andaru/afind