Fix some issues of FindPeakBackground

[Wenduo Zhou]

There are several issues or problems of algorithm FindPeakBackground.

1. It is not helpful for this algorithm to work on multiple spectra by single calling. So make FindPeakBackground operate on 1 spectrum a time.

2. FindPeaks may not use FindPeakBackground correctly. Verify and correct the error if there is any.

[Wenduo Zhou]

Refactored FindPeakBackground. Refs #9020.

1. Refactored and thus fixed some issues;
2. Added more unit tests;
3. Change input property. Algorithm can work with 1 spectrum only.

Changeset: 441a4bb8376cd2d0a0e2827b9d56807a71b9304f

[Wenduo Zhou]

Adapted to new algorithm property. Refs #9020.

Changeset: 8437353745febffa5f3aefc8f0b60c6a15e1c206

[Wenduo Zhou]

Make unit test to remove all genrated workspaces. Refs #9020.

Changeset: 1755937b270ea3853a823ff3a279ebec9fce3e4c

[Wenduo Zhou]

For tester

The changes in this ticket include a change in input property (WorkspaceIndices to WorkspaceIndex) and refactoring the code. The behavior of the algorithm should not change. What you can do:

• Check whether the unit tests and system tests are passed.
• Load some data with peaks and run the algorithm on it to find peaks' background.

[Peter Peterson]

At lines 123-124 you raise an exception if the workspace index is not specified. This is not necessary if the input workspace only has one spectrum.

[Wenduo Zhou]

Enable algorithm to accept 1 spectrum ws w/o. specify. Refs #9020.

Changeset: 6533dc128bd7bb3c5d84631b010a018d7964c338

[Peter Peterson]

Merge remote branch 'origin/feature/9020_fix_findpeakbkgd'

Full changeset: ​ec6563c3f5e6ff5f0f7c38ac133fc066e3c458d0

[Stuart Campbell]

This ticket has been transferred to github issue ​9863