[TASK] Deprecate wizardTab and icon attributes on Form

This change:

* Marks as deprecated in code and rendered documentation, the arguments `wizardTab` and `icon` on `flux:form` in favour of the `options` attribute which is an array that can contain a `group` (equivalent of `wizardTab`) and an `icon` member.
* Removes properties on `FluidTYPO3\Flux\Form` but leaves in place getter and setter with deprecation logging, redirects storage to `options` class member.
* Introduces `OPTION_*` constants on `FluidTYPO3\Flux\Form` which define supported options. Other extensions are expected to either use what is provided here or introduce own constants (as constants in their own extension's namespace).
Merge pull request #626 from NamelessCoder/deprecateoptions

[TASK] Deprecate wizardTab and icon attributes on Form