KNOWAGE-6894
KNOWAGE-6895
KNOWAGE-6896
Data Preparation implementation should be fully finished now, it needs to be confirmed working on latest1 because we dont have spark on our local env.

KNOWAGE-7111
Added an additional check inside Metaweb.

KNOWAGE-7114
Implemented custom formulas as requested inside Metaweb and QBE.
Changed KnCalculated field so it reads formulas from a property instead a descriptor, a new required property propCalcFieldFunctions needs to be passed to the component.

Possible bugfix: KNOWAGE-7103

Bugfix: KNOWAGE-7105

Merge branch 'sprint-15-bugfix' of https://github.com/vstanojevic/Knowage-Server into sprint-15-bugfix

Bugfix KNOWAGE-6958

Bugfix:

KNOWAGE-7115
KNOWAGE-7109

Possible bugfix:
KNOWAGE-7105

Bugfixes:
KNOWAGE-7112
KNOWAGE-7113