cmfm: secure storage and other improvements

This patch adds support for virtual filesystems and implements a SecureStorage
filesystem (a password protected area) mounted in /storage or /sdcard/storage
(in chrooted environments).
Also includes a better print support and a cleanup of the code and design of
the menu drawer.
Bump version to 2.0.0

Required: https://github.com/jruesga/android_external_libtruezip located
in external/libtruezip

Patchset 4: Fix selection of unmounted virtual storages.
            Fix actions on virtual mount points folders.
            Fix strings and typos. Change drop for delete secure storage.
Patchset 5: Move actionbar buttons to navigation drawer
            Remove history position
Patchset 6: Update theme preview images
            Fix filesystem status image on theme change
Patchset 7: Fix binary file detection in editor (including unicode files)
Patchset 8: Fix unsafe operations in virtual mountpoint logic
Patchset 9: Rebase

Change-Id: I65511352ca649dcbf238c8b07cf8c22465296e8e
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>