Pass profile directory as parameter to mkarchiso

archiso/mkarchiso:

Change all override option parameters (i.e. -A, -C, -D, -L, -P and -g) to not directly override the global variable they are tied to, but instead using an override_ prefixed variable.

Add _set_overrides() to use override_ prefixed variables (if set) to override those without a prefix.

Remove -B (a profile directory) from the list of parameters. The profile directory is now provided as separate non-option parameter.

Add a call to _read_profile(), _set_overrides() and command_build_profile() to the fallthrough option of the switch-case checking command_name - a non-option parameter to mkarchiso. This effectively provides the possibility to set the profile directory using a non-option parameter, while still maintaining compatibility to legacy named arguments used in the configs' build.sh scripts.

Extend the warning in regards to legacy build.sh based commands to mkarchiso by providing an EOL with archiso v49.

Change the help output to reflect the changes and further elaborate on the legacy commands used by build.sh scripts.

Change help output to be ordered alphabetically.

Add help output for -r and -g options.

Call _set_overrides() for legacy commands that accept one or more of the overriden options (i.e. command_init, command_install, command_prepare and command_iso).

configs/{baseline,releng}/build.sh:

Change call to mkarchiso to use the profile's directory as a named argument instead of an option-argument.

README.rst:

Fix documentation on how to call mkarchiso with a profile directory.

Fix wording and ordering of option arguments for run_archiso documentation.

Fixes #52 (closed)