Toolbar

Two toolbars, one for editor and other for the rendering window are added to give the user ease to select basic options and save time.

TODO:
* [x] Make the search&replace panel appear below the toolbar instead of above it
* [ ] This pull request contains the scintilla editor code (from pull request #879). Consider removing the scintilla commits to have a clean pull request. Otherwise we have to wait until #879 is merged.