Add support for free-text sections

[ammen99]

On IRC there was the suggestion to use alternative config format for Wayfire, more similar to Sway.

No matter what we think is better, even now we could use free-text sections, i.e sections which don't have the option = value format. This could be useful for ex. in autostart, potentially command (I don't really like how the pairs look like when editing the config file), etc.

Once activators are programatically callable (WayfireWM/wayfire#655) it would even be possible to write a plugin which receives a section of the config which looks like Sway's config. For example:

[my-super-cool-config-plugin]
bind "<super>KEY_T" plugin1/do_stuff; plugin/2_do_stuff
bind-signal "plugin1_signal" plugin2/do_stuff