Add save path for data folders tied to Experimentor

[kameyer226]

This ties into #53 .

Currently, saving data occurs in one file folder. At least in Windows 10, the searching of files in this single folder becomes slow as the number of scans builds up. It could be prudent to save files to folders as per the Experimentor (including a Default experimentor folder), permissions may then be settable as per Experimentor (Experimentor can for example lock out the folder for writing when he/she is not on the equipment), may also help with file backup service of the instrument.

Suggestion is to incorporate a filepath in the config tied to the Experimentor list, should not be necessary to create a filepath widget on the GUI. May be important to validate the filepath somehow prior to the start of a scan, or at least log whether the path is open for writing.

[ddkohler]

@kameyer226 in the meantime you can periodically clear the data folder (assuming your data folder is being backed up). Alternatively, you can move old data to another folder. I don't think we intended to keep all data permanently stored on the lab computer.