#68 tabulardata: New formula "ABSOLUTE_FREE"

[Ulrich Herbst]

the tabulardata library (used in the different xxxts-Tablespace size checks, the disk check, the lvmfreespace-check) knows just about comparisons in PERCENT.

We should add a comparison with an absolute free-value, e.g. you can than set a threshold, to hold 5 GByte in a tablespace free.