Modifies the displacement vectors but keeps the color bar consistent with displacement

[paskino]

Scales the displacement vectors by the UI vector scaling parameter and keeps the color bar in the range of the displacement.

• closes #245
• closes #251
• closes #271
• closes #272
• closes #181
• closes #133
• supersedes #261

[DanicaSTFC]

Tested on magma data and different point cloud files. it works. Only inp does not work. Opened issue https://github.com/TomographicImaging/iDVC/issues/273