Slighty improve javascript.

- use only one call of sql_select
- use only one call of sql_format
- use jQuery selector instead of getElementById to avoid js errors when
not found.
Merge pull request #183 from rjuju/fix_js

Slighty improve javascript.
Fix label of Reset button. Thanks to Julien Rouhaud for the report.
Update ChangeLog and version to 6.0
Fix typo
Add -B or --bar-graph command line option to use bar instead of line in graph. Thanks to Bart Dopheide for the suggestion. Also fix Checkpoint Wal files usage graph title.
- Fix issue in calculating min/max/avg in "General Activity" report. It was build on the sum of queries duration per minutes instead of each duration. Thanks to Jayadevan M for the report.
- The same issue remains with percentile that are build using the sum of duration per minutes and doesn't represent the real queries duration.
- This commit also include a modification in convert_time() method to reports milliseconds.
Fix automatic detection of rsyslogd logs. Thanks to David Day for the report.