Added Formatter for tables in Specs

I will also add a Table-Formatter for features. Should I add a preference page?

The formatter has a partial support for multiline cells:
- The expressions in the cells don't get formatted, preserving user formatting
- Spaces around multiline block added to ensure equal column widths

Example:

    | a | b       | c |
    | 1 | 1       | 1 |
    | 1 | 1 + 2 
            + 3+4 | 1 |
    | 1 | 1       | 1 |