WIP - 47 review models (#52)
WIP - 47 review models (#52)

* 1\Adding FundManagingBody (and changing Holding to point to it) - for funds that get bought and sold. 2\Adding comments to models

* Add Issuer FK to Security

* Fixinf docs.

hasadna/open_pension,hasadna/open_pension,hasadna/open_pension,hasadna/open_pension,hasadna/open_pension,hasadna/open_pension