fcm make: arguments as extra configurations

Each command line argument is considered a declaration line to append to the
configuration file.
test: fcm make options args
fcm make: extract: fix ssh location efficiency

Use file modified time instead of checksum.
Ignore hidden files.
Merge pull request #98 from matthewrmshin/fcm-make-extract-ssh-efficiency

fcm make: extract: fix ssh location efficiency
Merge pull request #96 from matthewrmshin/fcm-make-args

fcm make: arguments as extra configurations
fcm make: remove prev ctx as each step completes

This should reduce the memory footprint that was causing Perl to exit
with SIGSEGV.
Update CHANGES.md
Merge pull request #100 from matthewrmshin/fcm-make-prev-ctx-clear-out

fcm make: remove prev ctx as each step completes
fcm make: steps: don't inherit if already set

Hence, allow `steps=` to be declared before `use=`.

In addition:
* incr mode: on load of prev ctx, remove prev ctx of irrelevant steps.
* config unparse: `use=` before `steps=`.
Merge pull request #101 from matthewrmshin/fix-fcm-make-inherit-steps

fcm make: steps: don't inherit if already set