Spiderpig: Add output_line interaction with sensitive flag

Initial support for output_line() interaction, which has a flag to
indicate if the information is sensitive. For TerminalIO the line
is simply printed. For SpiderpigIO the line and sensitive flag are
passed through to the jobrunner which currently just logs the
sensitive lines in a prominent way. A followup commit will change the
jobrunner to log in a way that allows the sensitive information to be
excluded during log retrieval.

Use output_line() in scap/patches.py to output the sensitive
information about what patches are being applied.