Add a default constructor to the PCF and add a SetChannel method.

Allows reuse of a single PCF for different channels
Const correct methods and pointers for TPIs
Fix logic for no total number of pulses to draw
Add the PulseCandidateFinder to ExportPulse
ExportPulse now works with the PCF

Related to issues #172, #192 and #230
Merge branch 'feature/BK_PCF_in_ExportPulse' into develop