The class now only creates a fresh instance if:
 1. the current instance is empty (so on first use)
 1. It is about to execute, synchronously or asnchronously
 1. Execution has completed (here it just wipes the old instance, doesn't create a new one.)

This reduces the creation of algorithm instances to (1+1 nExecutions) per algorithm dialog
from (1 + nProperties + nExecutions).

This has merged in the changes from #12835 (keep open for alg dialog boxes)
as it is important for testing.

re #9480

Refs #10377

This reverts commit 8e55e36c.

Refs #10377

Refs #9059

Mainly removed Poco includes and used forward declarations instead.
Unsuprisingly this has affected some algorithms.
Refs #8784

If dropped from child algorithms they will be removed completely as
nothing else has a reference to them.
Refs #8412

The shared_ptrs held in WorkspaceProperty were set and still held by the
AlgorithmProxy object until it got knocked off the AlgorithmManager stack.
This gave the impression of a memory leak if an algorithm failed when
in fact the references were just being held too long.
Refs #8412

to algorithm base classes.
Refs #4218

Also some const-correctness.

The algorithm execute method dispatches the started notification so
no need to do it anywhere else.

Very annoying 9-character fix that took a long time to find, caused by the AlgorithmProxy, which is always causing trouble!

API side and also refs #4787 added to LoadLiveData

starts asynchronously

To fix SANS system tests

Fix a memory leak (well holding onto a shared_ptr too long) in the AlgorithmProxy after an algorithm has executed. Fixes #3560

Forgot the IAlgorithm and AlgorithmProxy changes - included now

Refs #2987. Fix issues with some code I wrote a while a go that shows up as a a warning on the Mac. Also cleaned up another prevalent warning from IMDGeometry.

Refs #3026:  Added a field for Wiki description to Algorithm. Made WikiMaker use it to generate wiki pages.

Added tests for correct alias.
refs #2823

Refs #2635. Algorithms can now stringize themselves and also construct themselves from a string. The format is AlgorithmName[.v](prop1=val1,prop2=val2,...), where the .v is optional and determines the version. Added convenience methods on the property manager to stringize itself as well.  

Blocking InstrumentWindow from accessing the instrument while an algorithm is running to prevent MantidPlot crashes. re #2133