Rust can compile to WASM, so let's use it for front-end code as well.
To compile the front-end:
```
cargo install cargo-web
cargo web deploy -p plume-front
```
Use uri! to generate links instead of hardcoded urls
Fix#110
Fix invalid links needing to be POST forms
Translate login message for boost and like directly from template
Put js for search in its own file
All the template are now compiled at compile-time with the `ructe` crate.
I preferred to use it instead of askama because it allows more complex Rust expressions, where askama only supports a small subset of expressions and doesn't allow them everywhere (for instance, `{{ macro!() | filter }}` would result in a parsing error).
The diff is quite huge, but there is normally no changes in functionality.
Fixes#161 and unblocks #110 and #273
