fixes #2153 - add trusted_puppetmaster_hosts setting to permit puppetmaster access

Connections to fact + report upload and externalNodes will be permitted from
any host listed in the trusted_puppetmaster_hosts setting, bypassing the
requirement for a registered smart proxy.

Setting model updated to support empty arrays for values and defaults.
fixes #2385 - use Capybara 2.0.x for Ruby 1.8 compatibility
fixes #2389 - Add basic support for plugin config to live in separate files
Added link to host on some audit entries
fixes failing test/fixture introduced in 7ff39bfa
flot charts

Use flot charts instead of highcharts.
flot charts license is more friendly.

This version of the code is feature compatible with the old charts,
including:
pie: drill-down and expend.
stacked charts: zoom, hide series in legend.
all types has tooltips.
etc.
Fixes #2378 Added Minitest and other code cleanups