Finalised centralisation within GAVPI.cs

Added VI_Profile.GetProfileFilename getter, making VI_Profile.ProfileFilename member string private, and updating GAVPI.cs, frmGAVPI.cs and frmProfile.cs to employ the getter.

Removed UI elements from VI_Profile.NewProfile, implementing them in GAVPI.NewProfile.

Updated frmGAVPI.newToolStripMenuItem_Click to take advantage of frmGAVPI.modifyToolStripMenuItem_Click.

Modified frmGAVPI.modifyToolStripMenuItem_Click to better acknowledge Profile edits.

Removed Profile edit checking (and offer of persistence) from VI_Profile.load_profile() and implmented them in GAVPI.LoadProfile.