Ability to configure all icons

[kartik-v]

Enhanced DynaGrid to include icon properties and allow configuring icon markups better for BS3 and BS4.

• iconVisibleColumn
• iconHiddenColumn
• iconSortableSeparator
• iconPersonalize
• iconFilter
• iconSort
• iconConfirm
• iconRemove

New static protected property $_icons which has default CSS classes for the icons for BS3 and BS4

protected static $_icons = [
    'iconVisibleColumn' => ['eye-open', 'eye'],
    'iconHiddenColumn' => ['eye-close', 'eye-slash'],
    'iconSortableSeparator' => ['resize-horizontal', 'arrows-alt-h'],
    'iconPersonalize' => ['wrench', 'wrench fa-fw'],
    'iconFilter' => ['filter', 'filter fa-fw'],
    'iconSort' => ['sort', 'sort fa-fw'],
    'iconConfirm' => ['ok', 'check'],
    'iconRemove' => ['remove', 'times'],
];