Refs #7789.  Refactored methods for estimation.

Refactored the methods to estimate peak background, peak range and peak
parameters.
Fixed a typo but critical. Refs #7789.
Adapted to new UI. Refs #7789.
Adapted to new UI. Refs #7789.
Turned back on previously failed unit tests. Refs #7789.
Resolved conflict. Refs #7789.