Add simple searchable column support for non-AJAX grids

idk maybe even AJAX grids can use?  not gonna try at the moment

tailbone/grids/core.py

@@ -76,6 +76,7 @@ class Grid(object):
                  enums={}, labels={}, assume_local_times=False, renderers={}, invisible=[],
                  extra_row_class=None, linked_columns=[], url='#',
                  joiners={}, filterable=False, filters={}, use_byte_string_filters=False,
+                 searchable={},
                  sortable=False, sorters={}, default_sortkey=None, default_sortdir='asc',
                  pageable=False, default_pagesize=20, default_page=1,
                  checkboxes=False, checked=None, check_handler=None, check_all_handler=None,
@@ -119,6 +120,8 @@ class Grid(object):
         self.use_byte_string_filters = use_byte_string_filters
         self.filters = self.make_filters(filters)
 
+        self.searchable = searchable or {}
+
         self.sortable = sortable
         self.sorters = self.make_sorters(sorters)
         self.default_sortkey = default_sortkey
@@ -241,6 +244,15 @@ class Grid(object):
                 kwargs['label'] = self.labels[key]
             self.filters[key] = self.make_filter(key, *args, **kwargs)
 
+    def set_searchable(self, key, searchable=True):
+        if searchable:
+            self.searchable[key] = True
+        else:
+            self.searchable.pop(key, None)
+
+    def is_searchable(self, key):
+        return self.searchable.get(key, False)
+
     def remove_filter(self, key):
         self.filters.pop(key, None)