Add d-ptr to kReportItemBase and port KReportItemLine

Summary:
Add a dptr and required accessors to KReportItemBase
and port KReportItemLine

Implement review comments

Removed need for KReportPosition and KReportSize classes

Implement more comments

Further porting of items

Further porting, Label designer item ported.

Some more structural changes, mainly around KReportDeisignerItemBase
gaining a d-ptr, and a pointer to the KReportItemBase so there is no
need to pass in individual pointers to the propertyset, size and
position.

Port remaining items to new api

Test Plan: Tested by opening/saving POI reports. rendering is as expected. compared XML before and after and size and position are the same

Reviewers: staniek

Reviewed By: staniek

Tags: KReport

Differential Revision: https://phabricator.kde.org/D3286