Change formatter to use normal papis configuration

Whereas before everything would be written in the `ref-format` string,
we can now simply put the customization options like any others passed
to papis - through its config file.

Comes with default options. Explanation added in README.

README.md

@@ -9,61 +9,74 @@ You can install from pypi with `pip install git+https://git.martyoeh.me/Marty/pa
 That's it! If you have papis and papis-bbt-formatter installed in the same environment (whether virtual or global),
 everything should now be installed.
 
-## Usage:
+## Usage
 
 In your papis configuration file (usually `~/.config/papis/config`), add the following under the main settings header:
 
-```toml
+```cfg
 [settings]
 formater = bbt
 ref-format = bbt
 ```
 
-For now, the ref-format *has* to start with `bbt`.
+For now, the ref-format also *has* to start with `bbt`. 
+
+Formatted reference keys by default will look like:
+
+`Harvey05briefhistoryneoliberalism` (for Harvey, D. (2005). A brief history of neoliberalism. Oxford New York: Oxford University Press.) 
+
+or `Harvey22reflectionsacademiclife` (for Harvey, D. (2022). Reflections on an academic life. Human Geography, 15, 14–24. doi:10.1177/19427786211046291)
+
+## Configuration
+
+No configuration except for the above setup is required for the formatting to work,
+but you can set a couple additional ones to customize the bevhavior to your liking:
 
 ### Title length
 
 Currently, you can change the length that the `TitleShort` in `Name2008TitleShort` will be cut down to by setting
-the maximum length in words or in characters.
+the maximum length in words `title-words=4` or in characters `title-chars=20` under the `[plugins.bbt-formatter]` section in your papis configuration file (usually located at `~/.config/papis/config`).
 
 To set a maximum word length, do:
 
-```toml
+```cfg
 [settings]
 formater = bbt
-ref-format = bbt[title-words=4]
+ref-format = bbt
+
+[plugins.bbt-formatter]
+title-words = 4
 ```
 
 In this case, the title will be shortened to 4 words maximum (the default),
 change the number to shorten/lengthen to your preference.
 Same idea for maximum character length:
 
-```toml
-[settings]
-formater = bbt
-ref-format = bbt[title-chars=10]
+```cfg
+[plugins.bbt-formatter]
+title-chars = 10
 ```
 
 This will allow a maximum of 10 characters for the title.
 Using both:
 
-```toml
-[settings]
-formater = bbt
-ref-format = bbt[title-words=4][title-chars=15]
+```cfg
+[plugins.bbt-formatter]
+title-words = 4
+title-chars = 20
 ```
 
 This will ensure a maximum of 4 words, however if they go more than 20 characters they will be cut off mid-word.
 You can set either option to `-1` to turn it off:
 
-```toml
-[settings]
-formater = bbt
-ref-format = bbt[title-words=4][title-chars=-1]
+```cfg
+[plugins.bbt-formatter]
+title-words = 4
+title-chars = -1
 ```
 
 This will ensure that a maximum of 4 words will be placed in the ref, but they do not have a maximum character length, 
-so will always be fully written out (the default behavior without title length options provided).
+so will always be fully written out (the default behavior if no title length options are provided).
 
 ---