Add support for multiple types db
Add LVM plugin
add percentile support to network traffic graphs

Set $CONFIG['percentile'] to a number and a XXth percentile line + legend
will be added to all network traffic (if_octets) graphs.

Closes #81
Merge remote-tracking branch 'feandil/for_upstream_lvm'
Merge remote-tracking branch 'dhchen/master'
type/base: replace array_merge by + sign to merge a fallback array

array_merge resets the index, while in case of $this->colors and
$this->legend, we'd like to keep the index. An irq plugin sample:
array(1 => 1, 'ERR' => 'ERR') must not become
array(0 => 1, 'ERR' => 'ERR') after an array_merge.
Revert "Use $CONFIG['time_range'] for default time range"

This reverts commit ea03070c24a1623067161374bed2e80021a06d97.
Wrong solution
Use config time_range for canvas graphs
Merge remote-tracking branch 'upstream/master'
Add an option to remove headers on host view
Add slab to memory plugin