* 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
* Searching '-mytag' will now exlude all shaares with 'mytag' tag.
* All tags starting with a '-' are renamed without it (through the Updater).
* Unit tests.
Minor code changes:
* LinkDB->filter() can now take no parameters (get all link depending on logged status).
* tagsStrToArray() is now static and filters blank tags.
* contains methods designed to be run once.
* is able to upgrade the datastore or the configuration.
* is based on methods names, stored in a text file with ';' separator (updates.txt).
* begins with existing function 'mergeDeprecatedConfigFile()' (options.php).
