Clean up section ids and classes

- all inputtypes should have id inputtype_${id}
- should have class capa_inputtype

common/lib/capa/capa/templates/crystallography.html

-<section id="textinput_${id}" class="textinput" >
+<section id="inputtype_${id}" class="capa_inputtype" >
      <div id="holder" style="width:${width};height:${height}"></div>
     <div class="script_placeholder" data-src="/static/js/raphael.js"></div>
     <div class="script_placeholder" data-src="/static/js/sylvester.js"></div>

common/lib/capa/capa/templates/textinput.html

 <% doinline = "inline" if inline else "" %>
 
-<%
-# TODO: 
-# Is id inputtype_${id} vs textinput_${id} important?
-# Is class capa_inputtype vs textinput important?
-# should really just use one.
-%>
-<section id="${'inputtype' if do_math else 'textinput'}_${id}" class="${'text-input-dynamath capa_inputtype' if do_math else 'textinput'} ${doinline}" >
+<section id="inputtype_${id}" class="${'text-input-dynamath' if do_math else ''} capa_inputtype ${doinline}" >
 
     % if preprocessor is not None:
     <div class="text-input-dynamath_data" data-preprocessor="${preprocessor['class_name']}"/>

common/lib/capa/capa/templates/vsepr_input.html

-<section id="vsepr_input_${id}" class="textinput" >
+<section id="inputtype_${id}" class="capa_inputtype" >
      <table><tr><td height='600'>
     <div id="vsepr_div_${id}" style="position:relative;" data-molecules="${molecules}" data-geometries="${geometries}">
     <canvas id="vsepr_canvas_${id}" width="${width}" height="${height}">