Allow form buttons to be themed by injected spans with specific class names around each button

Created a new common template which can be used to render buttons for any form. To convert a form...
Use:

Instead of:
{$form.buttons.html}

Buttons in 'converted' forms will be rendered w/ a surrounding <span> tag, and assigned a sequence of crm-button classes:
crm-button
crm-button-type-$btnType
crm-button$buttonName

Button types are: upload, next, back, refresh, cancel. We will be adding some specific css styles to differentiate back and cancel type buttons ('low priority').

Example:
<span class="crm-button crm-button-type-upload crm-button_qf_Main_upload">
<input type="submit" id="_qf_Main_upload" value="Confirm Contribution" name="_qf_Main_upload" class="form-submit default">
</span>

I've 'converted' the buttons in the following forms to use the new include:
templates/CRM/Contact/Form/Contact.tpl
templates/CRM/Contribute/Form/Contribution/Main.tpl
templates/CRM/Contribute/Form/Contribution/Confirm.tpl