Added parsing of exptime and period from master files (#256)

- New aare:to_string/string_to similar to what we have in
slsDetectorPackage
- Added members period and exptime to RawMasterFile
- Parsing exposure time and period for json and raw master file formats
- Parsing of RawMasterFile from string stream to enable test without
files

Comments:

- to_string is at the moment not a public header. Can make it later if
needed. This gives us full freedom with the API
- FileConfig should probably be deprecated need to look into it.
Meanwhile removed python bindings and string conv

RELEASE.md

@@ -7,6 +7,8 @@
 - Expanding 24 to 32 bit data
 - Decoding digital data from Mythen 302
 - added ``transform_eta_values``. Function transforms :math:`\eta` to uniform spatial coordinates. Should only be used for easier debugging. 
+- New to_string, string_to for aare
+- Added exptime and period members to RawMasterFile including decoding
 
 
 ### 2025.11.21