First pass at duckdb data interface

src/muse/data/example/default_new_input/commodities.csv

@@ -3,4 +3,4 @@ electricity,Electricity,energy,PJ
 gas,Gas,energy,PJ
 heat,Heat,energy,PJ
 wind,Wind,energy,PJ
-C02f,Carbon dioxide,energy,kt
+CO2f,Carbon dioxide,energy,kt

src/muse/data/example/default_new_input/demand_slicing.csv

@@ -1,7 +1,13 @@
-commodity_id,region_id,year,timeslice,fraction
-heat,R1,,night,0.1
-heat,R1,,morning,0.15
-heat,R1,,afternoon,0.1
-heat,R1,,early-peak,0.15
-heat,R1,,late-peak,0.3
-heat,R1,,evening,0.2
+commodity_id,region_id,year,timeslice_id,fraction
+heat,R1,2020,1,0.1
+heat,R1,2020,2,0.15
+heat,R1,2020,3,0.1
+heat,R1,2020,4,0.15
+heat,R1,2020,5,0.3
+heat,R1,2020,6,0.2
+heat,R1,2050,1,0.1
+heat,R1,2050,2,0.15
+heat,R1,2050,3,0.1
+heat,R1,2050,4,0.15
+heat,R1,2050,5,0.3
+heat,R1,2050,6,0.2

src/muse/data/example/default_new_input/timeslices.csv

@@ -0,0 +1,7 @@
+id,month,day,hour,fraction
+1,all-year,all-week,night,0.1667
+2,all-year,all-week,morning,0.1667
+3,all-year,all-week,afternoon,0.1667
+4,all-year,all-week,early-peak,0.1667
+5,all-year,all-week,late-peak,0.1667
+6,all-year,all-week,evening,0.1667