Deprecate browser-level fill(), type(), check(), uncheck()

[jsfehler]

Solution for:
#8
#162
#684

This PR adds a generic find method to replace the browser level actions. Currently it uses name, so the following are equivalent:

browser.fill('v', 'my_text')

browser.find('v').fill('my_text')

In 2021, find_by_name is significantly less useful than css or xpath. By exposing a generic find with an API for controlling which strategy is used, the browser level methods become unnecessary, but the shorthand style of writing scripts is preserved and made relevant for more people, eg:

browser.set_find_strategy('css')
browser.find('.my_css').click()
browser.find('.another_css').fill('some_text')

This also removes any need to deprecate find_by_x methods.

Roadmap:
#933

• Deprecate browser level actions
• Add generic find() method, defaults to find_by_name
• Add set_find_strategy() method to set find method. Allow name, xpath, css

Future:

• Remove browser level actions
• Default generic find to xpath, remove name
• Update documentation
• Write find() method tutorial