Command-line parsing

[minexew]

Should look something like: templeos-loader --drive=C,.,Writable --drive=D,SomethingElse -m 512 MyKernel.BIN

COMPILER and STARTOS can be still passed through env vars, since the loader is mostly agnostic to them (except for the issue outlined in #6)

[minexew]

Might be suitable:

• https://www.argtable.org/
• https://github.com/cofyc/argparse
• https://github.com/jamesderlin/dropt

[minexew]

-m option has not been implemented yet, but the framework is now in place