Adding Hjerson external metric

[pompomon]

The changes includes:

• externalMetrics/app/config/config.neon - I've added new metrics and setup connection to mysql
• externalMetrics/app/templates/Tasks/list.latte - I've updated color generation (so now it depends on the number of metrics and you don't need to add a color manually when adding a new metric)
• externalMetrics/external/hjerson+.py - external metric script
• externalMetrics/libs/Metrics/Hjerson.php - php-wrapper for external metric, I'll try to add some info to wiki today
• externalMetrics/www/css/bootstrap.min.css - small change, 1024px width instead of 940px, so all 8 metrics values fit (I'd propose to change it to % value)
• externalMetrics/schema.sql - file is now compatible with MySQL and has 4 more metrics

[martinpopel]

Fixes #14