Edit formula item on click brick

Added a item for editing a formula when a brick, which contains a formula is clicked.

edit (obusher)
Test: http://jenkins.catrob.at/job/Catroid-custom-branch-no-emma-test/180/
http://jenkins.catrob.at/job/Catroid-custom-branch-no-emma-test/201/
http://jenkins.catrob.at/job/Catroid-custom-branch-no-emma-test/202/