Improve typings for HOC's and fix imports

[schettino]

Closes: #565 #563 #562 #568 #571

• Fixed namespace type def and for when a extractor function is provided
• Removed unneeded default imports
• Improved types for hoc's

[coveralls]

Coverage remained the same at 76.645% when pulling 61815c5 on schettino:ts into b979553 on i18next:master.

[jvgreenaway]

These changes look good to me

[schettino]

@jamuhl whenever it's possible, we can release this patch

[jamuhl]

published in react-i18next@8.1.2

thanks a lot for the work done here

[Vrajmas]

Thanks, best regards