Add function ag_db_get_chart_list()
Add AgDbError error type
Add function ag_db_get_chart_data_by_id()

It loads one single chart from the database and fills an AgDbSave
struct with its data
Fix ag_db_select()

Using parameter @err for error collection was a bad idea. Creating
local_err instead.
Add function ag_chart_new_from_db_save()

It constructs an AgChart from an AgDbSave struct
Add list store model for the GdMainView
Add function ag_window_load_chart_list()

It loads all charts from the database and fills the main view’s list
store with it
Add libgd as a dependency and git submodule

libgd is required for GdMainView until MainView gets into Gtk (which I hope
will happen)
Create the GdMainView for the chart list

GdMainView doesn’t implement GtkBuildable yet, thus, it cannot be added
via the UI file.
Load chart list when opening a new window