Cleanup share by mail a bit

Cleanup share by mail a bit

* Moved to ned IBootstrap
* Register everything via the capabilities api (So clients can use it as
  well)
  - This applies to the enforcing passwords
* Updated the sharing js code to use it
* removed app.php
* removed unused settings now
* typehints
* strict typing

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>
Signed-off-by: npmbuildbot[bot] <npmbuildbot[bot]@users.noreply.github.com>
Signed-off-by: Morris Jobke <hey@morrisjobke.de>