bugfix: XY graph dialog layout order

* changed order of elements in XY graph dialog, because changing period
  resets start/end time -- user should choose period first.
Saving/loading time period in XYDialog

* added saving and loading time feature in XY graph dialog, saved time
  is kept after closing dialog, but not closing draw3.
Merge branch 'master' of github.com:Newterm/szarp