Optimizations

[hawken93]

Hi,

I've made some changes to make snorby run faster with a large database and offline.

Some of the changes like removing gravatar is probably not universally wanted and it would be better to actually make a global toggle for it.

Removing the signature activity from the event detail view may not be wanted either, but helps loading time.

You can test this by inserting about 500k-1 million events and running snorby on it.

• index "timestamp" column in event table
• remove gravatar
• remove signature activity from event details view, it is slow because of two count(*) queries
• signature events_count updating faster and without deadlock?
• faster top 5 signatures query

The first and the last two changes listed may be of universal usefulness :)

Let me know what you think, and I'll update the PR :)