renamed and documentation

* renamed to all lowercase
* added documentation
* added examples

core/modules/filters/get_index.js

@@ -1,5 +1,5 @@
 /*\
-title: $:/core/modules/filters/getIndex.js
+title: $:/core/modules/filters/getindex.js
 type: application/javascript
 module-type: filteroperator
 

editions/tw5.com/tiddlers/filters/examples/getindex.tid

@@ -0,0 +1,7 @@
+created: 20150203140000000
+modified: 20150203140000000
+tags: [[getindex Operator]] [[Operator Examples]]
+title: getindex Operator (Examples)
+
+<<.operator-example 1 "[[$:/palettes/Vanilla]getindex[background]]" "returns the value at index ''background'' of the [[DataTiddler|DataTiddlers]] [[$:/palettes/Vanilla]]">>
+<<.operator-example 2 "[tag[$:/tags/Palette]getindex[background]]" "returns all background colors defined in any of the ColourPalettes">>

editions/tw5.com/tiddlers/filters/getindex.tid

@@ -0,0 +1,17 @@
+created: 20150203140000000
+modified: 20150203140000000
+tags: [[Filter Operators]] [[Field Operators]]
+title: getindex Operator
+caption: getindex
+purpose: returns the value at an index of DataTiddlers
+
+<$macrocall $name=".operator-def"
+input="a [[selection of titles|Title Selection]]"
+parameter="the name of an [[index|DataTiddlers]]"
+paramName="i"
+output="the values at index <<.place f>> in each of the input titles"
+/>
+
+Each input title is tested in turn. If the corresponding tiddler is a [[DataTiddler|DataTiddlers]] and has the index <<.place i>> defined, its value is appended to the output.
+
+<<.operator-examples "getindex">>