* added "--bdist-base" option to parameterize where we build
the RPM (comes from "bdist" by default: "build/bdist.<plat>")
* simplified/cleaned up some code in 'run()' in the process of
removing (most) hard-coded directory names
* if "--spec-only", drop spec file in "dist" rather than "redhat"
(directory name still hard-coded, though)
* use 'reinitialize_command()' to fetch the "sdist" object to
tweak before running "sdist" command
* use 'self.copy_file()' method rather than 'copy_file()' function
* cosmetic tweaks to comments, error messages
* help strings start with lowercase
* added affirmative version of '--no-clean' and '--no-rpm-opt-flags',
which are the default (thus the attributes that correspond to
the options are now 'clean' and 'use_rpm_opt_flags')
* Command method 'find_peer()' -> 'get_finalized_command()'
* Command method 'run_peer()' -> 'run_command()'
Also deleted the 'get_command_option()' method from Command, and
fixed the one place where it was used (in "bdist_dumb").