Print plugin fit to bounding box option

When you activate this option, the print preview is fixed to the actual bounding box and hides the scale.

This commit adds neccesary changes to:

* PrintProvider.js
* PrintPage.js
* PrintMapPanel.js
* PrintPreview.js
* Print.js

Yo can activate this option in Print plugin with  `"bboxFit": true` in mapStoreConfig.js.

This pull request fixes #241
Merge pull request #259 from alediator/241_print_preview

Print plugin fit to bounding box option