refactor error handling

there have been some missing class definitions in the
other PR. Now fixed.
updated .gitignore
Merge pull request #27 from sumcumo/refactor_error_class

Refactor error class
merged pull request
Merge branch 'sumcumo-update_gitignore'
added settings menu site header
added default role generator on site create
Merge remote-tracking branch 'upstream/master'