Option to limit inline display of linked tables

Added a new option to smartgrid: "max_linked_inline".
When set to a value greater than zero, it will limit the inline display of linked tables (in grid, edit and details).
In case there are a number of linked tables greater than the setting, the links will be displayed in a select list menu.
Merge pull request #478 from alexdba/master

Option to limit inline display of linked tables