Fix check for incorrect number of export arguments
Fix some errors and warnings from pylint
Use klass instead of self for some classmethods
Disable axis menu when axis cannot be created
Remove warnings for sip by using new syntax (sip 4.12+)
Update copyright year
Only allow certain types of datasets to be editable.
Use 1-based index for picking
Fix ignoring error in exception dialog.

Before the whole exception with traceback and variables was used to
check uniqueness. Now just use traceback.
Allow non-text datasets to be used for labels
Add Numbers->Text dataset plugin. Fix bug when renaming datasets in Data->Edit.
Fix python3 problem
Add xgrid/ygrid params for 2D data, which will be used for non-linear spacing
Allow contours to use xgrid/ygrid
Fix image with new Dataset2D
When editing dataset names / widgets, do not clear name
Add notes field to doc, page and graph widgets. Add icon for doc.
Fix height of notes widget when opened
Add python implementation of image rescaling
Implement linear resampling in C++