Doc: Document min/max operators for lists

	Clist is similar to a set, except that unlike other sets, it can be

	modified. The type is used for community list (a set of pairs) and for

	cluster list (a set of quads). There exist no literals of this type.

	There are three special operators on clists:

	There are special operators on clists:

	<cf><m/C/.len</cf> returns the length of clist <m/C/.

	<cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute (for

	example <cf/bgp_community/). Similarly for <cf/delete/ and <cf/filter/.

	<cf><m/C/.min</cf> returns the minimum element of clist <m/C/.

	<cf><m/C/.max</cf> returns the maximum element of clist <m/C/.

	Operators <cf/.min/, <cf/.max/ can be used together with <cf/filter/

	to extract the community from the specific subset of communities

	(e.g. localpref or prepend) without the need to check every possible

	value (e.g. <cf/filter(bgp_community, [(23456, 1000..1099)]).min/).

	<tag><label id="type-eclist">eclist</tag>

	Eclist is a data type used for BGP extended community lists. Eclists

	are very similar to clists, but they are sets of ECs instead of pairs.