Add wildcards to each search token

[marijoo]

This PR resolves #47 by adding a new config setting wildcard_all_tokens which defaults to false and a setting wildcard_min_length which defines a minimum length for tokens before wildcards are applied.

I migratet the phpunit XML to the new version. If this is undesired, let me know and I will revert the commit.

Excerpt from the config file:

This setting controls whether all tokens of a search query shoudld be
handled using a wildcard instead of an exact match. This basically
means that for a search input of "hell wor", the query will match
documents containing "hell%" or "wor%" where % is the SQL wildcard of
a "like" condition. The wildcard will only be applied for
search tokens that have a minimum length of `wilcard_min_length`.
     
Setting this to `true` will add a wildcard to the end of each search
token. You may also set this to "both" to add wildcards to the beginning
and the end of each search token, for example: "%hell%" and "%wor%.
       
Note: Please not that changing this setting may negatively impact the
performance of search queries. Also you might want to make sure that
`require_match_for_all_tokens` is set to `false` when using this.

I added some test cases:

 ✔ Does not find documents if wildcard all tokens is disabled and no exact match is given
 ✔ Finds documents if wildcard all tokens is enabled and no exact match is given
 ✔ Finds documents if wildcard all tokens is set to both
 ✔ Does not find documents by wildcard if minimum token length is not reached
 ✔ Finds documents by wildcard if minimum token length is reached
 ✔ Adds wildcard to last token even if minimum length is not reached

[Namoshek]

Thanks, looks good so far! Just some minor points that need adjustment

[Namoshek]

Thank you!