Force split-view when two paths specified in args

Thanks to filterfalse.
Correct view switch when vifm gets only one path

Didn't switch if pane was already at specified path.
Extract load_scheme() from main()

Loads color scheme.  Converts old format to the new one if needed.
Terminates application with error message on error.

Also added new line character in error message (fputs() doesn't add one
automatically, only puts() does).
Extract convert_configs() from main()

Converts old versions of configuration files to new ones.
Terminates application with error message on error or when user
chooses to do not update anything.

Also added new line character in error message (fputs() doesn't add one
automatically, only puts() does).
Include stdio.h in vifm.c
Merge branch 'split-on-startup-with-two-arguments'

Force split view when vifm is started with two arguments on
command-line.  Also fix pane switch for one argument and move part of
code out of the main() function.