1) Do not add UI specific fields in install_config which is not used
at execution state, such as custom partition internal information.
Use only install_config['partitions']
2) Do not overwrite install_config['disk'] by partitions data.
Create new field for that: install_config['partitions_data']
3) New class pastitionpane as a sub element of custom partitioning
screen.
4) Rename PartitionISO to CustomPartition to avoid confusion.
5) Cleanup Image Builder.
Change-Id: Id1aef8b18b866ee464bd583c820f92c5037aae71
Reviewed-on: http://photon-jenkins.eng.vmware.com:8082/8105
Tested-by: gerrit-photon <photon-checkins@vmware.com>
Reviewed-by: Anish Swaminathan <anishs@vmware.com>
Alexey Makhalov