Make output from --checkconfig=snippets more useful

[mjordan]

Currently, if --checkconfig=snippets or --checkconfig=all finds a problem with a mapping snippet, it provides the following output:

./mik --config=bcss.ini --checkconfig=all
Commencing MIK.
PHP Fatal error:  Uncaught exception 'mik\exceptions\MikErrorException' in /home/mark/Documents/hacking/mik/mik:73
Stack trace:
#0 [internal function]: {closure}(2, 'DOMDocument::lo...', '/home/mark/Docu...', 98, Array)
#1 /home/mark/Documents/hacking/mik/src/config/Config.php(98): DOMDocument->loadXML('<originInfo><pl...')
#2 /home/mark/Documents/hacking/mik/src/config/Config.php(51): mik\config\Config->checkMappingSnippets()
#3 /home/mark/Documents/hacking/mik/mik(78): mik\config\Config->validate('all')
#4 {main}
  thrown in /home/mark/Documents/hacking/mik/mik on line 73

This is way too verbose and not very helpful in resolving the problem. It would be if we can provide more user-friendly and helpful output.