Import lates changes from Sergey Linev

Here are some of the latest changes:
1. First try to handle resize of canvas in the browser, for the
   moment works only with collapsible layout
2. Also first try to interactively move separation line between
   browser and drawing field.
3. Small fix of minor ticks drawing on the axis
4. Introduce display class for MDI drawing. Provide two implementations -
   'collapsible' for old kind and 'tabs' for new kinds.
5. Adjust size of color palette drawing when labels would take more place as provided.
6. Add correct filling of statistic for TProfile, fix small problem with underflow/overflow bins.
7. Provide way to select display kind ('collapsible', 'tabs') in the simple GUI.

For the complete list of changes, see etc/http/changes.txt