fixed css issue in filterbar hlist when list-style-image is used
some html output code style fixes
added option to change dateformat in event new/edit form
complete rewrite of date handling in new/edit event form and validating the given data

For date validation only the standard SQL date format e.g. 2014-01-31
will be used. For displaying another date format can be used, but this
data will not be used directly.
moved admin settings page styles to css file; fixed some style issues
preparation for version 0.6.2
Merge branch 'develop'