tag groups
renamed to just 'Taggable'
Refactor details region
Tree - add find node by regexp/substring

Fixes #29
Added server roles support

Adds classes/methods for setting up server roles in configuration -> settigns.
The whole configuration section has very dense and deep structure - this patch
attempts to reflect this by adding directory/file structure which will allow us
to add more config pages in future without causing too big mess.

Fixes #11
Fix pylint-reported errors
initial testing, integrated accordion into pxe page

trying treeaccordionitem

testing
added configuration button to /regions/taskbar/center.py; added
select_dropdown to page.py

added select_dropdown
added test_infra_template

renaming template now works

selection now works

adding template now works

the test is now done and works

some renaming done
added test_infra_pxe_server

some additional finishing touchés
added test_infra_refresh_pxe_server

removed sleep

now asserts for expected image names

removed some unuseful commented lines
added test_infra_management_systems

mngmnt systems -> add new now works
new waiting for refresh in test_infra_refresh_pxe_server