Improvements to Index

Changes to Index app:
- date/time format
- overall visual changes
- removed Search box for the moment, as it only works with PlainPost messages

Solved https://github.com/privly/privly-applications/issues/31
Renamed Index to History + changed Chrome context menu 
This PR includes improvments to index, renaming apps and solving iss31. I left that PR opend there just for the conversation, and I'll close it when this PR is merged.