Merge branch 'heatmap-panel' of https://github.com/alexanderzobnin/grafana into alexanderzobnin-heatmap-panel

* support panel repeat for datasource template variable

* support All option

This seems to work for the three use cases:

- Overflow on the left
- Overflow on the right
- Elements that are out of view on page load

* use utf8mb4 character set for connections to mysql

* use utf8mb4 character set for tables, shorten varchar fields used in unique indexes

* migration type to update table character set

* update table character sets

* set charset for temp_user.status

* gofmt

Fix some spelling/grammar/wording problems in What's New in Grafana v4.0