File Manager: Folder zipping / archive support

* App version: 2.12
* Android version/rom: 14.x

## Explain the Problem
Markor has lots of filemanager capabilities, but one thing I see recurringly missing / in need is:
support for archiving - so to zip & unzip.

This issue is about implementing such a feature to Markor's filemanager, to create archives from selection, and to unarchive to a selected destination.

As of supported formats, zip can be enough to support at the start (and is even part of the Java standard library). One important point is to stay in JVM (i.e. no p7zip/libarchive native dependency that would require ABI specific builds).

Start by locating Markor's file manager implementation, including its selection and destination flows. Review Java's standard-library ZIP support and define the behavior for creating an archive from selected files and extracting it to a selected destination; done means both zip and unzip work in the Android file manager without a native dependency.

Written by the indexing model from the issue text.