Major rewrite of the setting handling system!

Added = as a generic settings management command, no more single terminal
commands for each setting.
Added default/allowed values to the default config.
Removed the window position settings.
Cleaned up check_config() in read_config(), slightly less horrible now.
Probably something else I forgot...
Switched from local common to libsyntyche's common
Added goto_line-cmd (fixes #42)
Changed create_ui to use libsyntyche
Added automagic config load/save (fixes #32)

On activation of Kalpana's window, the config is loaded.
Whenever a setting is changed in the terminal, the config is saved.
The theme is (probably?) not affected by this (you still need rt).