Fix parsing of --config argument with whitespace

[pcahyna]

Uses argv properly instead of concatenating all arguments in a single string and searching for the --config argument inside it.

Fixes also some other corner cases:

• The "--config " string in the middle of another arguemnt is not interpereted as a --config argument anymore.
• "--confg" argument is not accepted anymore (used to be an alias for --config).

Before:

• did --help --conf "System roles/sconf.did"

Create at least a minimum config file /home/pcahyna/.did/System:
[general]
email = Name Surname <email@example.org>
 ERROR  Unable to read the config file '/home/pcahyna/.did/System'.

• did --help --email "Samuel--conf <sconf@example.com>" --conf "System roles/sconf.did"

Create at least a minimum config file /home/pcahyna/.did/<sconf@example.com>:
[general]
email = Name Surname <email@example.org>
 ERROR  Unable to read the config file '/home/pcahyna/.did/<sconf@example.com>'.

• did --help --confg "test/sconf.did"
  <help text>

After:

• did --help --conf "System roles/sconf.did"
  <help text>
• did --help --email "Samuel--conf <sconf@example.com>" --conf "System roles/sconf.did"
  <help text>
• did --help --confg "test/sconf.did"

Create at least a minimum config file /home/pcahyna/.did/config:
[general]
email = Name Surname <email@example.org>
 ERROR  Unable to read the config file '/home/pcahyna/.did/config'.

[sandrobonazzola]

Can you please add also a test for this?

[pcahyna]

I can, but it will take me some time.