Refactor capture.c

[nrwahl2]

There are a number of issues:

• Values such as parameter mins and maxes are hard-coded.
• Argument parsing is custom and handles only positional arguments. It expects six of them.
  • We should at least use argp or getopt. However, we could use GOption since GLib is already installed on the oresat-dev image.
• There are no default values. Defaults would make running the program much simpler in the common case.
• There are several calls to atoi()/atof() (notoriously problematic).
• There are float equality comparisons, which may fail even if the values ought to be the same. Floats are actually unnecessary in these cases.
• main() is monolithic. There are likely opportunities to functionize pieces of it for maintainability and for isolation of variables.
• Input validation and error reporting could be improved.
• Others that I'm sure we'll notice after we address the above and look more closely.

There are also plenty of opportunities to generally clean up the code, to improve function documentation, and to standardize the style. I'm partial to the C style recommendations here: https://clusterlabs.org/pacemaker/doc/2.1/Pacemaker_Development/html/c.html

(Full disclosure, Pacemaker is software that I help maintain.)