Allow user to define the search function

[dasDaniel]

Currently the searchValue function returns a string that svelteTable compares internally to the search term. This is limiting the search functionality and prevents the user from defining search options like starts with or is case sensitive.

Instead the function should take the row and the search term as parameters and return a boolean. This will allow more flexibility in defining the search behaviour.

This change should allow both ways of using searchValue for backwards compatibility.

TODO:

• add support for searchValue(row:Object, searchTerm:string):boolean
• maintain support for searchValue(row:Object):string
• update search example (Example5)
• update docs and include deprecation warning

[dasDaniel]

Released in v0.5.3: #122

[Saibamen]

121