Relates to https://github.com/shaarli/Shaarli/issues/324
Added:
- `SessionManager` class to group session-related features
- unit tests
Changed:
- `getToken()` -> `SessionManager->generateToken()`
- `tokenOk()` -> `SessionManager->checkToken()`
- inject a `$token` parameter to `PageBuilder`'s constructor
Signed-off-by: VirtualTam <virtualtam@flibidi.net>
