Fix for button alignment

This is a fix for the button vertical alignment which was not implemented as of yet. The solution is based partly on XSoftBG code fragements, and has then further been enhanced.

The following screenshots show the behaviour before and after the fix. The rows/columns have the following settings:
Column 1: Only text
Column 2: Only image
Column 3: Text and image
Column 4: Text and image (textAlignment middle)
Column 5: Text and image (textAlignment right)
Row 1-3: Default alignment (null value)
Row 4-6: Horizontal center alignment
Row 7-9: Right alignment
Row 10-12: Center/bottom alignment

BEFORE:
![alignment_before](https://f.cloud.github.com/assets/3050757/654560/3c19c08c-d4fe-11e2-80c7-ca21517deee6.png)

AFTER:
![alignment_corrected](https://f.cloud.github.com/assets/3050757/654561/40841a32-d4fe-11e2-9d7e-e8b55524c8c3.png)