* translation system and unit tests
* Translations everywhere
Dont use translation merge
It is not available with PHP builtin gettext, so it would have lead to inconsistency.
Fixes#784
From now, searching for tags with an empty value will return only not tagged links,
with the search bar showing `x results [not tagged]`.
Note that using the api, the searchtags request parameter must be set to `false` to get the same result.
- [ ] Update API doc
All existing link will keep their permalinks.
New links will have smallhash generated with date+id.
The purpose of this is to avoid collision between links due to their creation date.
* search type now carried by LinkDB in order to factorize code between different search sources.
* LinkDB->filter split in 3 method: filterSearch, filterHash, filterDay (we know what type of filter is needed).
* filterHash now throw a LinkNotFoundException if it doesn't exist: internal implementation choice, still displays a 404.
* Smallhash regex has been rewritten.
* Unit tests update
