[AutoComplete] Support onFocus and onBlur events propagation

[zandroid]

It's required to use onFocus and onBlur events over AutoComplete component:
<AutoComplete ... onFocus={this._handleInputFocus} onBlur={this._handleInputBlur} />

These events are propagated to TextField from AutoComplete props but are overwritten by custom handlers. So we need to support them obviously.

[newoga]

@zandroid I'm not sure if this is as simple as it looks yet. I started this effort once when I started working with the project but the <AutoComplete/> is currently written in a way where the focus has to be reset each time the input changes. It leads to these events being called excessively. We could add these but it may not work the way you think it does. Maybe you can try it a bit and see if it still has that behavior.

[zandroid]

@newoga Probably you are right. I am using warkaround right now:
<div onBlur={...}><AutoComplete ... /></div>
And sometimes it works strange. I will take a look at this fix more detailed.

[newoga]

@zandroid Feel free to quickly review this PR: #2338

Ultimately we'll probably have to improve the way focus is handled in the <Menu /> component to solve this once and for all.

[oliviertassinari]

@zandroid Thanks for opening this PR but the issue is now closed with #3356.