Uses forward declarations where possible.
Refs #8784

The ADS is now generating a node tree that describes the state
of the ADS when queried. This in turn queries the workspace itself
and while running in MantidPlot an executing script can cause
things wrapped in a cow_ptr to be copied and at the same time
access the pointer while it is being copied, causing a crash.

Refs #7583

Added an entry in configservice. Harmonized the 'pick a color map' dialogs to one method.

and plotting. Too much debugging output

when cloning a workspace. So explicitely declared the copy constructors of every class up to DataItem.

To fix segfaults on destruction. Multiple virtual inheritance is hard ;)

Also Refs #996: starting to clean up Algorithm.execute()