remove "search in this collection" slot in virtual collections

[GVogeler]

mom-ca offers a general "search in this collection" widget in the collections / fonds menu. In aggregated collections like https://www.monasterium.net/mom/DO/collection and in collections with hooked-in charters this does not work as search uses the current collcetion/fonds identifier for constraint.
Entry point to code:

mom-ca/my/XRX/src/mom/app/charters/widget/goto-search.widget.xml

Lines 150 to 160 in 8dc9a2b

	<div>
	<xrx:i18n>
	<xrx:key>search-in-collection</xrx:key>
	<xrx:default>Search in this collection</xrx:default>
	</xrx:i18n>
	<form style="padding:0;" action="{conf:param('request-root') }search?">
	<input id="search-field" name="q" type="text" value="{request:get-parameter('q', '')}"/>
	<input type="hidden" name="context" value="{$wgoto-search:id}"/>
	<input id="search-trigger" type="submit" value="{i18n:value('search', $xrx:lang, 'Search')}"/>
	</form>
	</div>

[GVogeler]

There are probable two options:

1. remove this slot in case of aggregated collections
2. include a computed index methods (exist-trigger) to create an internal representation of these aggregationes

The second solution could also solve the problem with hooked-in charters, but it is a substantial effort. I would therefore prefer the first.