JFG-737
Merge https://github.com/griddynamics/jagger into JFG-738

Conflicts:
	dbapi/src/main/java/com/griddynamics/jagger/dbapi/DatabaseServiceImpl.java
+ implement scenery of downloading file
+ IO Storage interface + in memory implementation
+ add FileDownloader class to hide interaction with callbacks
+ PlotRepresentation know what metricNode it represented
+ implement idea - one MetricNode = one PlotSeriesDto
- plot id is needed only for markings that are not really needed in current implementation
+ download file without pop up new window
+ Download service
+ ability to save trends as csv plots
prototype of menu bar in plot panels
optional attribute 'delay' is added to load-user-group(s)
JFG-738
session scope plots have been added to the webUI
with follow features:

-Tests are sorted by startime
-Pause between end of previous test and next test also considered
+ csv file generator : flush / close in finally block
- remove useless methods from ControlTree class
+ more meaningful messages, log error on exception while cvs file creation
+ rename InMemoryNewFileStorage -> InMemoryFileStorage
Merge branch 'grid_master' into JFG_785_menu_bar_in_PlotNodes
minor changes
Merge branch 'JFG_780_test_summary_in_PDF_via_dbservice' of https://github.com/dlatnikov/jagger into JFG-738_new
negative metrics are correctly displayed now
Merge branch 'grid_master' into JFG_772_negative_values_in_plots
merge with master
TestInfoDTO was expanded with endTime and moved to FetchUtil
Unchecked session scope plots are fixed
TaskDataDto has ids and sessionIds connected now
decision based on limits is using only matched baseline now