Filemanager feature: Basic archiving support (i.e. zip)

[gsantner]

• 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).