NFC Code cleanup to core task class

[mattwire]

Overview

Just commenting and variable renaming towards making this more generic.

Identified during investigation for dev/core#158

Technical Details

CRM_Core_Form_Task::preProcessCommon() is currently only used by CRM_Case_Form_Task.

[civibot]

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[colemanw]

Where is this used?

[eileenmcnaughton]

I couldn't find any instances?

[mattwire]

https://github.com/civicrm/civicrm-core/pull/12316/files#diff-8e58e0ef24ffee40975a92a797f7acecR135

It's a baby step towards making that preProcessCommon function generic enough to handle more than just the case task.

[eileenmcnaughton]

Just a testing note - this messes with the $useTable variable so we need to check that it is still possible to export more than 500 contacts - eg from manage groups and normal searches only retrieve the first 500

UPDATE I confirmed useTable not used here

[eileenmcnaughton]

@mattwire I worked through this refactor locally & it makes sense. It changes 'queryMode' to be more correct - does that fix any bug? And if so is there something still needing backporting to the rc?

I'm merging this but can we follow up by adding a getter on queryMode ?

$form::getQueryMode();

is, IMHO, less ugly than

$form::$queryMode