clean up of acquire_widget and metadata_widget

-condense button enabling and disabling code during scan and goto
-increase SampleID max length to 11 characters
added *.bak to .gitignore
-added QSettings configuration
-added config package and gratings_config module, and began
implementing a basic persistent configuration using QSettings
-added configure_gratings_widget module, and began implementing the
user interface
added HardcodedGratingsConfig

This will act as a simple substitute until I have a chance to add menus
for actually configure the grating.
finished implementing

-added grating checks to Acquirer
-finsihed HardcodedGratingsConfig
-fixed small spectrometer driver bug
Merge branch 'feature-auto-select-grating'