bitbake: toastergui: streamline construction of filter objects

In line with comments from review, remove the QuerysetFilter
class (redundant) and convert ProjectFilters into a class
with static methods.

[YOCTO #8738]

(Bitbake rev: 59379bf6467029223045c5ebef868729d8e02c86)

Signed-off-by: Elliot Smith <elliot.smith@intel.com>
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/toaster/toastergui/widgets.py

@@ -32,7 +32,6 @@ from django.template import Context, Template
 from django.core.serializers.json import DjangoJSONEncoder
 from django.core.exceptions import FieldError
 from django.conf.urls import url, patterns
-from toastergui.querysetfilter import QuerysetFilter
 
 import types
 import json