(temporary?) fix for measurement_step_max key error in thellier_gui auto interpreter with older data sets
prevent error in SPD get_delta_pal
prevent thellier_auto_interpreter from breaking when get_PI_parameters fails (original case: tmin different in t_Arai and zdata_temperatures, typo in original data).  this causes the auto_interpreter to skip the messed up data.
fix error in curvature calculation (if there is no curve, you can't calculate curvature...)
	deleted:    arch3k.py
	deleted:    cals3k.py
	deleted:    cals3k_4b.py
	modified:   igrf.py
	modified:   pmag.py => fixed some bugs in doigrf model calculations
Merge branch 'master' into menubar

Conflicts:
	thellier_gui.py
QuickMagic step 3 filling in additional data basically works, except that it fails to propagate down into er_samples.txt.  need to fix this
QuickMagic step 3: help message and extra grid columns for check er_samples round II