Minor UI improvements/bugfixes for Scenario

This item contains a list of general UI bugs to be fixed:
Use grey borders for all the grid and not only for the header Fixed in DROOLS-2684
Add some padding to the cells of the grid Fixed in DROOLS-2684
Add some padding to right panel the tab titles
Remove scrolling bar from right panel Fixed in DROOLS-3170
Review expression editor component HTML/CSS (paddings, indents, etc)
Review right panel padding (now it is hardcoded)
Use text area inputs instead of text box for inline editing
Reduce the width of Index column Fixed in DROOLS-3167