Add basic classes outlining backup process.
Need implementation of UI
Setup UI implementation of Backup creation
Add buffers to (hopefully) faster performance
Add basic classes outlining restore process.
Need implementation of UI
Attaching everything to the UI level
Prompt users to backup before upgrading
Merge pull request #31 from Doplgangr/ZipBackup
Add dialogs to places where long processes involving vault I/O would occur.
Edit change passphrase dialog to new design
Changed FragmentPagerAdapter to FragmentStatePagerAdapter

- Made ImageLoadJobs cancelable

The FragmentStatePagerAdapter allows old Fragments to be removed from
the memory. This allows nearly unlimited browsing through images without
memory issues.
Reduced the number of background jobs

This might be a temporary solution, but it avoids out of memory bugs
when scrolling very fast trough pictures. (too many ImageLoadJobs
running at the same time)
Add dialogs to places where long processes involving vault I/O would occur.