front: Move script tag at the end of the base template

This should normally allows for a quicker page loading.
fix: The avatars croppers disappeared when re-uploading an image
feature: Allows to attach two avatars to a character

There are two sizes: one large (180x400) and one small (100x100). To
get these two avatars, we use croppie.js which is a pretty awesome
front: Improve the appearance of characters avatars
refactor: Clean-up a bit the result of previous commits
fix: Select the first created character to be the default one
feature: Implement a persistent characters selection

Some notable facts about this patch:
* We now use Semantic UI (css/js framework)
* There is now a new user column to remember the current character
feature: Display the list of Characters of a connected User
refactor: Simplify the migrations with one psql user only
feature: Let users create new characters
feature: Improve the navigation on the website
refactor: Move the Html renderer as a feature in the galatian crate

This may be an opinionated implementation, and we could improve it by
parameterizing the classes used in the html attributes.
feature: Implement a persistent session at log in

The logic is heavily inspired by the implementation of Plume.
feature: Create a new route to render a galatian document

We rely on maud, a nice template engine, to generate the final
html. The logic of parsing and generation is implemented in a
dedicated crate using the nom library.
feature: Give a different message when login with a new account
feature: Create an account on login in case of unknown nickname

With this patch, the `login/` route always try to insert a new entry
in the users table. Because of the new uniqueness constraint on the
nickname column, the call fails when the nickname is already used;
this error is handled, the other error kinds results in an error 500.
feature: Implement a new dummy route /login

This root will only get the value of the form, and redirect you
directly to the index. Once there, a small message is displayed, with
the name you have chosen.

This is *not* persistent, unfortunately. But it is only a matter of
refactor: Divide index tera template with a reusable base template

This will be useful in the future, to deal with future
routes. Currently, this get ride of the footer, with the commit
revision mention.
feature: Print the current git commit revision in each pages

This can allows user to know which version of ogmios they are
currently using.
refactor: Use count instead of load+len

The previous implementation was probably less efficient, because the
table entries were loaded from the database, and a Vec was created,
only to call the len method.