Adding columnized output support to "PredefinedOptions" tag [5.2.1-RC1]

The "PredefinedOptions" tag is the core of all form controls, where user can select something from predefined set of options. For example:

inp_edit_options - dropdown with a list of options
inp_edit_radio - list of radio buttons
inp_edit_checkboxes - list of checkboxes, where multiple checkboxes can be selected at once

The tag is good at what it does, but when it comes to more advanced stuff (see list below), then it's pretty hard to it.

displaying list of options split across several columns
displaying only selected options
both from above combined

Typical PredefinedOptions tag usage the in template

<inp2:m_DefineElement name="checkbox_option_element">
	<li>
		<inp2:m_Param name="option"/>
	</li>
</inp2:m_DefineElement>
 
<ul>
	<inp2:unit-prefix_PredefinedOptions field="FieldName" block="checkbox_option_element" selected="selected"/>
</ul>

Parameters added for "PedefinedOptions" tag

Parameter Name	Parameter Description
selected_only	display only selected options (without this all options will be displayed)
columns	indicate column count to split displayed options into

Also now the "selected" parameter default to "selected" value, when no given explicitly in tag. This would allow to write less code to do same task as before.

Parameters added to block, specified in "block" parameter to "PredefinedOptions" tag

Parameter Name	Parameter Description
column_number	currently printed column number
column_changed	flag, that is only set when a column change occurs (let "block" to decide how to handle that)
option_number	order number of the option in the list (starting from 1)
option_count	total option count that will be printed

Usage examples

For we're having following options list:

Option Key	Option Title
100	Option One
200	Option Two
300	Option Three
400	Option Four
500	Option Five

Using "columns", "column_changed" and "column_number" parameters

<inp2:m_DefineElement name="checkbox_option_element">
	<inp2:m_if check="m_Param" name="column_changed">
		</ul>
		<ul class="column-<inp2:m_Param name='column_number'/>">
	</inp2:m_if>
	<li>
		<inp2:m_Param name="option_number"/>. <inp2:m_Param name="option"/> (key: <inp2:m_Param name="key"/>)
	</li>
</inp2:m_DefineElement>

<ul class="column-1">
	<inp2:unit-prefix_PredefinedOptions field="FieldName" block="checkbox_option_element" columns="3"/>
<ul>

The example from above would produce following output:

<ul class="column-1">
	<li>1. Option One (key: 100)</li>
	<li>2. Option Two (key: 200)</li>
<ul>

<ul class="column-2">
	<li>3. Option Three (key: 300)</li>
	<li>4. Option Four (key: 400)</li>
<ul>

<ul class="column-3">
	<li>5. Option Five (key: 500)</li>
<ul>