Many lines were not conformant with the project's formatting rules.
This patch should fix all formatting and whitespace issues in the code
base.
A clang-format directive was put around the connect() calls containing
SIGNALs and SLOTs whose signatures would be denormalized because of the
formatting rules.
Introduce missing CustomData-attributes of KDBX4 format to allow
storing of plugin data for groups and entries - adopt Metadata to use
the same storage mechanism
Add simple view for CustomData as part of EditWidgetProperties
Tracking of CustomData-Modification using SIGNAL-SLOT update-mechanism
