Created some icons and modified drawer

Now the app shows the actions that will/might be available in the end result. Icons such as: lock & hide, unlock & show, shred, etc. Things left to do:
- add icons to drawer next to items
- make dividers in drawer to separate categories
- make drawer more pretty, e.g. show little dividers in drawer
- fix share icon as it has a slightly different style
- make contextual actions smarter: only show lock & hide if all selected files are shown and unlocked and vice versa