copy first multi val to single val on save. fixes #43

method for getting all pages known to struct

moved schema listing to central place

moved validation to its own class

the validator class is partly test covered through the entry tests but
dedicated tests might be helpful

Enable sorting by mutiple columns

adjusted active filter output

correct summary output

let PageColumns always have the same fq label

streamline sort direction handling

we now use a boolean everywhere

correctly apply dynamic params to the search config

some form fixes for the dynamic filters

moved the filter reducing to Search

flatten array returned for URL parameters

added tests for dynamic parameters

make sure page columns have a label

schemas and columns need to be known before init dyn params

renamed methods for more coherence

major refactoring of the whole table aggregation

this is still completely untested

make dynamic parameters a bit better to handle

Now the aggregation class no longer needs to juggle around with ugly
strings but can simply call functions on the SearchConfigParameter class
to genera

make dynamic parameters a bit better to handle

Now the aggregation class no longer needs to juggle around with ugly
strings but can simply call functions on the SearchConfigParameter class
to generate new parameters.

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new option to select distinct data through search

this is useful for aggregating exisitng data regardless of page context

filters need to be their own group in the SQL

make column context available to types

This allows renderers to access the column info. Eg. the tag type will
need the column's name to set up a filter parameter

added field hints #29

made methods public again, protected was wrong

fix some assignment bugs and add tests #35