Allow user to set Q and wavelength min/max before merging and Q min/max before PDFFourierTransform in POLARIS scripts

[RichardWaiteSTFC]

Describe the solution you'd like
This issue has three sub-parts:

1. Add optional new parameters to allow user to crop data to Qmin and Qmax before call to PDFFourierTransform in POLARIS scripts
   

   mantid/scripts/Diffraction/isis_powder/polaris_routines/polaris_algs.py

   Line 122 in 94276f6

   pdf_output = mantid.PDFFourierTransform(

2. Optional Qmin/max to crop the data in each bank prior to merging

3. Optional wavelength min/max to be applied to all banks

[RichardWaiteSTFC]

Update from Gabriel Perez

We would actually like the following two capabilities besides being able to set a Qmin and Qmax for the PDFFourierTransform:

• Being able to select specific Qmin and Qmax for each individual banks that will provide new cut off values before the banks are merged in step 16 (maybe after or instead step 8?). This is because sometimes, we'll want to narrow the ranges of some individual banks to get rid of noisy data at the extremes.
• Being able to provide a wavelength range to use for all banks (also before the merge to obtain S(Q)). This is because some samples have resonances that fall within the range that Polaris gets and we may want to cut those off. As these resonances are wavelength dependent, they will be present in every bank, so a single lambda min and lambda max for all banks should be enough.