Merge pull request #1 from Ensembles/master

Updates from main
Merge pull request #2 from Ensembles/master

dl lib on linux only
Added state_map implementation
Added enum realisation_state_enum
Added state_map_size() function
Added methods to state_map + locking
state_map completed with state_map_equal() and state_map_fwrite()
Added state_map_fread() to read into an existing instance
state_map_fread() will reset the map if file not found
Added function site_map_update_undefined() which will only update undefined values
Added state_map_select_matching() function
Changed meas_data to only allocate for the number of active ensemble members
Updated test enkf_state_map()
ADded state_map_deselect() + state_map_select_matching() will only modify explicitly matching elements
Merge branch 'master' into enkf-handle-killed-realisations
Added new functions to the state_map
Changed include path
Changed enkf update to take a mask of realisations
Merge remote-tracking branch 'upstream/master' into enkf-handle-killed-realisations
Removed unused variable