html5 placeholder attribute

[john-07]

add line: placeholder Ztal_Tales_Form.getAttrib:element,string:placeholder
for support this attribute

<!-- Will display an <input> element -->
<input metal:define-macro="inputElement"
       tal:attributes="type Ztal_Tales_Form.inputType:element;
                       name name | element/getFullyQualifiedName;
                       id element/getId;
                       class Ztal_Tales_Form.getAttrib:element,string:class;
                       value value | nothing;
                       maxlength Ztal_Tales_Form.getAttrib:element,string:maxlength;
                       checked checked | nothing;
                       autocomplete Ztal_Tales_Form.getAttrib:element,string:autocomplete;
                       disabled Ztal_Tales_Form.isDisabled:element;
                       placeholder Ztal_Tales_Form.getAttrib:element,string:placeholder"
/>

[ChrisAnstey]

This has been added on the 'develop' branch now, so will be merged in to the master branch on the next release.