Small bug fixes and improvements

SardineReborn

Bug fixes:

• Able to load *sgt files that are erroneous for the model panel
• When saving a *sgt file, the err column is at minimum 0.000001

Improvements:

• Added grid and zoom improvements on the picking window
• Warning when trying to pick a negative time

Future improvements:

• Picking multiple traces at once (line picking)
• Offset support improvements
• Shifting by numerical value (preview?)
• Changing seg2 files header for the interface