Handle data saving edge cases properly

[MichaelHuth]

Situation 1:

• Experiment is untitled, NWB saving is enabled in DAEPhys panel
• On acquire nwb save dialog pops up and asks for nwb name (NWB_PrepareExport) -> User chooses cancel
• sweep acquisition runs and finishes another nwb save dialog pops up (NWB_AppendSweepDuringDAQ) -> User chooses a file

-> Only last sweep gets saved in NWB.

Situation 2:

• Acquisition is setup with a locked DAEPhys panel, data was already saved to a device specific NWB file
• User changes or adds a stimset through the wavebuilder

-> stimset changes are not saved to the NWB

Situation 3:

• Acquisition is done with a single device "Device1" (locked DAEPhys panel, NWB saving enabled) -> NWB file without device suffix is created
• Another device is locked in a second DAEPhys panel and acquisition is done ("Device2") -> NWB file with device suffix "Device2" is created
• DAEPhys panel of "Device1" gets unlocked -> NWB file without device suffix is closed
• DAEPhys panel of "Device1" gets locked and acquisition is done -> NWB file with "Device1" suffix is created where through NWB_PrepareExport all previous sweeps (i.e. the ones already saved in the first file without device suffix) are saved.