separate settings.ini.php for default config

when using LHC from git it may cause conflicts when settings get updated.

changes:
- let the installation script try to write to the settings directory instead of the settings.ini.php
- rename the settings.ini.php to settings.ini.default.php
- erConfigClassLhConfig will load the settings.ini.default.php if settings.ini.php is missing

this ensures, that for new installations(where settings.ini.php is missing) the the default values will be loaded during installation, but they will be saved to settings.ini.php that is loaded then.

you might want to update your [upgrading guide](http://livehelperchat.com/article/view/63).